Remove the breakpoint set in TestCallConcurrent so that it doesn't
interfere with the call injection protocol.
The fact that it can is a bug but that bug is better addressed after
PRs #1503 and #1504 are merged, this keeps tests happy in the meantime.

Fixes #1542

Go 1.12 introduced a change to the internal map representation where
empty map cells can be marked with a tophash value of 1 instead of just
0.

Fixes #1531

RestoreRegisters on linux would also restore FS_BASE and GS_BASE, if
the target goroutine migrated to a different thread during the call
injection this would result in two threads of the target process
pointing to the same TLS area which would greatly confuse the target
runtime, leading to fatal panics with nonsensical stack traces.

Other backends are unaffected:

- native/windows doesn't store the TLS in the same CONTEXT struct as
  the other register values.
- native/darwin doesn't support function calls (and wouldn't store the
  TLS value in the same struct)
- gdbserial/rr doesn't support function calls (because it's a
  recording)
- gsdbserial/lldb extracts the value of TLS by executing code in the
  target process.

Add options to the stack command to read the goroutine ancestors.
Ancestor tracking was added to Go 1.12 with CL:
https://go-review.googlesource.com/c/go/+/70993/

Implements #1491

* *: use loglevel to control what gets logged instead of output redirection

This stops logrus from doing all the formatting just to discard it
immediately afterwards.

* logflags: replace default formatter of logrus

The default formatter of logrus emits logs in two different formats
depending on whether or not the output is going to a terminal. The
output format for non-terminals is indented to be machine readable, but
we mostly read logs ourselves and the excessive quoting makes that
format unreadable.
When outputting to terminals it uses ANSI escape codes unconditionally,
without checking whether the terminal it is connected to actually
supports colors.

This commit replaces the default formatter with a much simpler
formatter that always uses a more readable format, doesn't use colors
and places the key-value pairs at the beginning of the line (which is a
better match for how we use them).

* cmd/dlv: add command line options to redirect logs

Adds two options, --log-to-file and --log-to-fd, to redirect logs to a
file or to a file descriptor.

When one of those two options is specified the "API server listening
at:" message will also be redirected to the specified file/file
descriptor.
This allows clients that want to use the "API server listening at:"
message to do so even if they want to redirect the target's stdout to
another file or device.

Implements #1179, #1523

Adds initial support for plugins, this is only the code needed to keep
track of loaded plugins on linux (both native and gdbserial backend).

It does not actually implement support for debugging plugins on linux.

Updates #865

The lookup at it.pc-1 is only ever done if fn is not nil and pc !=
fn.entry. Also when it happens only the File and Line fields are
allowed to change.

Like we do with unrecovered panics, create a default breakpoint to
catch runtime errors that will cause the program to terminate.
Primarily intended to give users the opportunity to examine the state
of a deadlocked process.

runtime.clone (on some operating systems?) work similarly to fork:
when a thread calls runtime.clone a new thread is created. For a
short period of time both the parent thread and the child thread
appear to be running the same goroutine, until the child thread
adjusts its TLS to point to the correct goroutine.

This means that proc.GetG for a thread that's currently running
'runtime.clone' could be wrong and, consequently, the field
proc.(G).thread of a G struct returned by GoroutinesInfo could be
also wrong. And, finally, that FindGoroutine could sometimes return
a *G with a bad associated thread if the goroutine of interest
recently called 'runtime.clone'.

To work around this problem this commit makes two changes:

1. proc.GetG will return nil for all threads executing runtime.clone.
2. FindGoroutine will return the selected goroutine as long as the
   ID matches the one requested.

Change (1) takes care of the 'runtime.clone' problem. If we stop
the target process shortly after a thread executed the SYSCALL
instruction in 'runtime.clone' there are three possibilities:

a. Both the parent thread and the child thread are stopped inside
'runtime.clone'. In this case the state we report is slightly
incorrect, because both threads will be reported as not running any
goroutine when we do know which goorutine one of them (the parent)
is running. This doesn't actually matter since runtime.clone is
always called on the system stack and therefore the goroutine in
runtime.allgs will have the correct location.

b. The child thread managed to exit 'runtime.clone' but the parent
thread didn't. This is similar to (a) but in this case GetG on the
child thread will return the correct goroutine. GetG on the parent
thread will still return (incorrectly) nil but this doesn't matter
for the samer reason as described in (a).

c. The parent thread managed to exit 'runtime.clone' but the child
thread didn't. In this case GetG will return the correct goroutine
both for the parent thread (because it's not executing runtime.clone)
and the child thread.

Change (2) means that even if a thread has a completely nonsensical
TLS (for example because it's set through cgo) evaluating a variable
with a valid GoroutineID will still work as long as it's the current
goroutine (which is the most common case). This change also doubles
as an optimization for FindGoroutine.

Fixes #1469

Fixes #1481

Fixes #1493

Go 1.6 is now unsupported by the Go team and 3 years old and
runtimeTypeToDIE can use some simplification.

Do not mention external debug info files when the problem might just be
that the executable was stripped.

When compression is applied by default running the DWZ tool on the
resulting binary will crash.

The actual default compression code will look and see if compression
makes any difference and if so replace the normal `.debug_*` section
with `.zdebug_*`. This is why it may not have been hit before. On one of
my workstations I build with 1.12rc1 and no compression happens, but on
a Fedora VM I build and the binary results in compressed DWARF sections.

Adding this flag will make this test more consistent overall.

Fixes #1471

This file should be located elsewhere (on the OSX host, I believe) and
as such does not beed to be checked in here.

Fixes #1460

FindGoroutine can be slow when there are many goroutines running. This
can not be fixed in the general case, however:

1. Instead of getting the entire list of goroutines at once just get a
   few at a time and return as soon as we find the one we want.

2. Since FindGoroutine is mostly called by ConvertEvalScope and users
   are more likely to request informations about a goroutine running on a
   thread, look within the threads first.

The allg cache was corrupted when the count parameter was actually
reached.

Fix the bug and add a test for this.

The repository is being switched from the personal account
github.com/derekparker/delve to the organization account
github.com/go-delve/delve. This patch updates imports and docs, while
preserving things which should not be changed such as my name in the
CHANGELOG and in TODO comments.

Some build environments (such as when building RPMs) enjoy symlinking
things. This unfortunately causes our tests to fail as we record the
path of fixtures and use that when looking up file:line information.
However, the debug info in the binary records the original file
location, not the location of the symlink.

When casting an integer into a struct pointer we make a fake pointer
variable that doesn't have an address, maybeDereference and
structMember should still work on this kind of Variable.

Fixes #1432

PTRACE_GETREGSET was added in Linux 2.6.34, running this request in an
older kernel will report EIO, as documented on the manpage.

Fixes #1197

The size of the TLS memory arena needs to be aligned to pointer sized
boundaries on 86x64 architectures, otherwise some programs using cgo
will not have the correct offset for the g struct.

No tests because reproducing this problem depends on behavior of the
GNU ld linker caused by unclear influences.

Fixes #1428.

Goroutine id == 0 is special (there can be many goroutines with id 0).
If the caller of FindGoroutine asks for gid==0 and current thread is
running a goroutine 0 (i.e. either no goroutine or a special
goroutine) return whatever goroutine is running on the current thread.

Updates #1428

The fix in 7f53117e for Issue #1416 had a bug, fix it and add a test.

Fixes #1419

Minidumps are the windows equivalent of unix core files.
This commit updates pkg/proc/core so that it can open and read windows
minidumps.

Updates #794

Move windows register handling code to winutil package in preparation
for using it in proc/core to read minidump files.

If a function can be inlined it will appear as two entries in
debug_info. A DW_TAG_subprogram entry with DW_AT_inlined = true (that
will be used as the abstract origin) and a second DW_TAG_subprogram
entry with an abstract origin.
To retrieve the name of this second entry we must load its abstract
origin.

If proc.Step encounters a CALL instruction that points to an address
that isn't associated with any function it should still follow the
CALL.

The circumstances creating this problem do not normally occur, it was
encountered in the process of fixing a bug created by Go1.12.

It was never true that return variables were in the inverse order.
Instead in Go1.11 return variables are saved in debug_info in an
arbitrary order and inverting them just happened to work for this
specific example.

This bug was fixed in Go 1.12, regardless we should attempt to
rearrange return variables anyway.

When a location expression requests a register check that we have as
many bytes in the register as requested and if we don't report the
error.

Updates #1416

Instead of unconditionally returning all present goroutines,
GoroutinesInfo now allows specifying a range (start and count). In
addition to the array of goroutines and the error, it now also returns
the next goroutine to be processed, to be used as 'start' argument on
the next call, or 0 if all present goroutines have already been
processed.

This way clients can avoid eating large amounts of RAM while debugging
core dumps and processes with a exceptionally high amount of goroutines.

Fixes #1403

This patch is a slight refactor to share more code used for genericprocess initialization. There will always be OS/backend specificinitialization, but as much as can be shared should be to preventduplicating of any logic (setting internal breakpoints, loading bininfo,etc).

Users can create sparse maps in two ways, either by:
a) adding lots of entries to a map and then deleting most of them, or
b) using the make(mapType, N) expression with a very large N

When this happens reading the resulting map will be very slow
because loadMap needs to scan many buckets for each entry it finds.

Technically this is not a bug, the user just created a map that's
very sparse and therefore very slow to read. However it's very
annoying to have the debugger hang for several seconds when trying
to read the local variables just because one of them (which you
might not even be interested into) happens to be a very sparse map.

There is an easy mitigation to this problem: not reading any
additional buckets once we know that we have already read all
entries of the map, or as many entries as we need to fulfill the
MaxArrayValues parameter.

Unfortunately this is mostly useless, a VLSM (Very Large Sparse Map)
with a single entry will still be slow to access, because the single
entry in the map could easily end up in the last bucket.

The obvious solution to this problem is to set a limit to the
number of buckets we read when loading a map. However there is no
good way to set this limit.
If we hardcode it there will be no way to print maps that are beyond
whatever limit we pick.
We could let users (or clients) specify it but the meaning of such
knob would be arcane and they would have no way of picking a good
value (because there is no objectively good value for it).

The solution used in this commit is to set an arbirtray limit on
the number of buckets we read but only when loadMap is invoked
through API calls ListLocalVars and ListFunctionArgs. In this way
`ListLocalVars` and `ListFunctionArgs` (which are often invoked
automatically by GUI clients) remain fast even in presence of a
VLSM, but the contents of the VLSM can still be inspected using
`EvalVariable`.

Adds a config file option to allow specifying a list of directories to
search in when looking for seperate external debug info files.

Fixes #1353

Make code in core.go OS and architecture agnostic in preparation for
adding Windows minidump support.

The linux version of proc/native and proc/core contained largely
overlapping implementations of the register handling code, deduplicate
it by moving it into proc/linutil.