More untangling. Arch doesn't actually need to know anything about a
Goroutine.

This is going towards untangling proc in order to clean it up.

Cleanup some unused members.

* proc: fix stacktraces when a SIGSEGV happens during a cgo call

When a SIGSEGV happens in a cgo call (for example as a result of
dereferencing a NULL pointer) the stack layout will look like this:

(system stack) runtime.fatalthrow
(system stack) runtime.throw
(system stack) runtime.sigpanic
(system stack) offending C function
... other C functions...
(system stack) runtime.asmcgocall
(goroutine stack) call inside cgo

The code in switchStack would switch directly from the
runtime.fatalthrow frame to the first frame in the goroutine stack,
hiding important information.

Disable this switch for runtime.fatalthrow and reintroduce the check
for runtime.mstart that existed before this version of the code was
implemented in commit 7bec20.

This problem was reported in comment:
https://github.com/go-delve/delve/issues/935#issuecomment-512182533

* cmd/dlv: actually disable C compiler optimizations when building

* scripts: use relative path in gen-cli-docs.go

Makes gen-cli-docs.go work outside GOPATH.

* Documentation,cmd/dlv: tidy up --help output

The description of --log-dest, --log-output and --backend is very
verbose and messes up the output of --help, move it to two "additional
help" subcommands.

* alias stepout to so

* run gen-cli-docs.go to update cli/README.md

For some reason the version of dwz in Travis-CI now fails to run on Go
binaries. Ignore the particular error.

* *: Add .cirrus.yml for FreeBSD testing

* *: run go mod tidy

* service/test: prefer 127.0.0.1 over localhost

* dwarf/line: fix TestDebugLinePrologueParser

* vendor: rerun go mod vendor

* terminal/command: add support for next [count]

* disallow negative counts.

* handle github comments, and regen docs.

* Fix the fact that we don't print the file info in the last step of the next count.

* Fix a typo, cleanup a few other observations.

Implements #1640

GCC produces DW_TAG_inlined_subroutine entries without a
DW_AT_abstract_origin attribute.
From the bug report:

 <1><1fe6c7c>: Abbrev Number: 41 (DW_TAG_subprogram)
    <1fe6c7d>   DW_AT_external    : 1
    <1fe6c7d>   DW_AT_name        : (indirect string, offset: 0x485814): MultiGetImpl
    (omissis)
 <2><1fe6c9e>: Abbrev Number: 65 (DW_TAG_inlined_subroutine)
    <1fe6c9f>   DW_AT_low_pc      : 0x311023a
    <1fe6ca7>   DW_AT_high_pc     : 0x5
    <1fe6caf>   DW_AT_call_file   : 10
    <1fe6cb0>   DW_AT_call_line   : 1690
 <2><1fe6cb2>: Abbrev Number: 20 (DW_TAG_inlined_subroutine)
    <1fe6cb3>   DW_AT_abstract_origin: <0x1ffb534>
    <1fe6cb7>   DW_AT_entry_pc    : 0x311023f
    <1fe6cbf>   DW_AT_ranges      : 0xe9bf20
    <1fe6cc3>   DW_AT_call_file   : 10
    <1fe6cc4>   DW_AT_call_line   : 1690

Inlined subroutine at 1fe6c9e doesn't have abstract origin, a name or a
declaration location. It's unclear whether this is in-standard and what
it even means.

Let's ignore it.

Fixes #1636

Propagate signals when stepping because debugserver will report them,
from the issue:

2019-07-11T16:31:25+02:00 debug layer=gdbconn <- $z0,105525d,1#c9
2019-07-11T16:31:25+02:00 debug layer=gdbconn -> $OK#00
2019-07-11T16:31:25+02:00 debug layer=gdbconn <- $vCont;s:c41c3#50
2019-07-11T16:31:25+02:00 debug layer=gdbconn -> $T1cthread:c41c3;threads:c41c3,c41d7,c41d8,c41d9,c41da;thread-pcs:105525d,7fffc464bf46,7fffc464bbf2,7fffc464bbf2,7fffc46...
2019-07-11T16:31:25+02:00 debug layer=gdbconn <- $Z0,105525d,1#a9
2019-07-11T16:31:25+02:00 debug layer=gdbconn -> $OK#00

in this case we request a single step on thread c41c3 but debugserver
reports instead a signal (in this case SIGWINCH).

Fixes #1610

* add max-variable-recurse parameter

* Add --continue to continue process on launch/attach

* Add small test of --continue

* regenerate usage docs

* minor cleanup

* Use similar approach to `trace` and connect and detach using a client instance

* back out previous attempt

* regen usage doc

* fix up continue test

* fix TestContinue to properly test --continue

* back out unnecessary changes

* update faq

If we return ErrProcessExited we should also set exited to true.

Go 1.13 insists on adding a go version to go.mod, add one that makes
sense.

Add variables flag to mark variables that are allocated on a register
(and have no address) and variables that we read as result of a
function call (and are allocated on a stack that no longer exists when
we show them to the user).

Increases the maximum string length from 64 to 1MB when loading strings
for a binary operator, also delays the loading until it's necessary.

This ensures that comparison between strings will always succeed in
reasonable situations.

Fixes #1615

* FreeBSD initial support

* first code review fixes

* regs slice upd

* execPtraceFunc wrap

* disabled concurrency tests
fixed kill() issue

* disabled concurrency tests
fixed kill() issue

* cleanup vendor related code

* cleanup ptrace calls

* vendoring latest changes

* Revert "vendoring latest changes"

This reverts commit 833cb87b

* vendoring latest changes

* requested changes

Remove dependancy on glide and instead switch completely over to using
`go mod vendor` as our vendor solution.

Support for rev {next,step} is not currently implemented.

Fixes #1598

Backports debug/dwarf commit: 535741a69a1300d1fe2800778b99c8a1b75d7fdd
CL: https://go-review.googlesource.com/18459

The x/debug/dwarf that we used for dwarf/godwarf/type.go was forked
from debug/dwarf long before this commit.

Original description:

    Currently readType simultaneously constructs a type graph and resolves
    the sizes of the types. However, these two operations are
    fundamentally at odds: the order we parse a cyclic structure in may be
    different than the order we need to resolve type sizes in. As a
    result, it's possible that when readType attempts to resolve the size
    of a typedef, it may dereference a nil Type field of another typedef
    retrieved from the type cache that's only partially constructed.

    To fix this, we delay resolving typedef sizes until the end of the
    readType recursion, when the full type graph is constructed.

Fixes #1601

If the argument of 'source' ends in '.star' it will be interpreted as a
starlark script.
If the argument of 'source' is '-' an interactive starlark repl will be
started.

For documentation on how the starlark execution environment works see
Documentation/cli/starlark.md.

The starlark API is autogenerated from the JSON-RPC API by
script/gen-starlark-bindings.go.
In general for each JSON-RPC API a single global starlark function is
created.
When one of those functions is called (through a starlark script) the
arguments are converted to go structs using reflection. See
unmarshalStarlarkValue in pkg/terminal/starbind/conv.go.
If there are no type conversion errors the JSON-RPC call is executed.
The return value of the JSON-RPC call is converted back into a starlark
value by interfaceToStarlarkValue (same file):

* primitive types (such as integers, floats or strings) are converted
  by creating the corresponding starlark value.
* compound types (such as structs and slices) are converted by wrapping
  their reflect.Value object into a type that implements the relevant
  starlark interfaces.
* api.Variables are treated specially so that their Value field can be
  of the proper type instead of always being a string.

Implements #1415, #1443

* proc: allow simultaneous call injection to multiple goroutines

Changes the call injection code so that we can have multiple call
injections going on at the same time as long as they happen on distinct
goroutines.

* proc: fix EvalExpressionWithCalls for constant expressions

The lack of address of constant expressions would confuse EvalExpressionWithCalls

Fixes #1577

* tests: fix tests for Go 1.13

- Go 1.13 doesn't autogenerate init functions anymore, tests that
  expected that now fail and should be skipped.
- Plugin tests now need -gcflags'all=-N -l' now, we were probably
  getting lucky with -gcflags='-N -l' before.

* proc: allow signed integers as shift counts

Go1.13 allows signed integers to be used as the right hand side of a
shift operator, change eval to match.

* goversion: update maximum supported version

* travis: force Go to use vendor directory

Travis scripts get confused by "go: downloading" lines, the exact
reason is not clear. Testing that the vendor directory is up to date is
a good idea anyway.

Support for bulk queries makes the DWARF quality checker
(github.com/dr2chase/dwarf-goodness/cmd/dwarf-goodness)
run much more efficiently (replace quadratic cost with
linear).

The location specified '<fnname>:0' could be used to set a breakpoint
on the entry point of the function (as opposed to locspec '<fnname>'
which sets it after the prologue).
Setting a breakpoint on an entry point is almost never useful, the way
this feature was implemented could cause it to be used accidentally and
there are other ways to accomplish the same task (by setting a
breakpoint on the PC address directly).

Also fixes findCompileUnitForOffset which was broken in some edge cases
(when looking up an offset inside the last child of the compilation
unit) which don't happen in normal executables (we only look up types, and those
are always direct childs of compile units).

Allow changing the value of a string variable to a new literal string,
which requires calling runtime.mallocgc to allocate the string into the
target process.

This means that a command like:

    call f("some string")

is now supported.

Additionally the command:

    call s = "some string"

is also supported.

Fixes #826