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.

Some tests used a fake vendor directory placed inside _fixtures to
import some support packages.
In go.mod mode vendor directory are only supported on the root of the
project, which breaks some of our tests.
Since vendor directories outside the root of the project are so rare
anyway it's possible that a future version of go will stop supporting
it even in GOPATH mode.
Also it was weird and unnecessary in the first place anyawy.

For some reason the Go file pkg/dwarf/reader/reader.go had the exec bit
set on it. This patch removes that.

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.

This patch allows the `trace` CLI subcommand to display return values of
a function. Additionally, it will also display information on where the
function exited, which could also be helpful in determining the path
taken during function execution.

Fixes #388

Some libraries (for example steam_api64.dll) will send this exception
code to set the thread name on Microsoft VisualC.
In theory it should be fine to send the exception back to the target,
which is responsible for setting a handler for it, in practice in some
cases (steam_api64.dll) this will crash the program. So we'll mask it
instead.

Fixes #1383

Fixes #1378

Adds an --exec flag for the trace subcommand allowing users to specify a
pre-compiled binary to exec and trace.

Also adds a --test flag as a convienance for compiling and tracing a
test binary.

Fixes #1073

Fix a bug where the regexp would be used as a package string
incorrectly. This would manifest when trying to execute the trace
subcommand as `dlv trace <regexp>` without specifying a package
identifier. The `<regexp>` would be passed to the Go build command
causing an error.

ContinueOnce didn't detect the way RR signals that it has reached the
start of the process and would never finish.

Fixes #1376

Continue did not resume execution after a call to CallFunction if the
point where the process was stopped, before the call CallFunction, was
a breakpoint.

Fixes #1374

The name "where" may confuse users into thinking that this parameter
actually does something where in fact it's just arbitrary text used to
identify the checkpoint.

Fixes #1373

Add ability to evaluate variables on the scope of a deferred call's
argument frame.

Fix escape checking in function calls  and add a flag to disable it.

Extend `string()`
1.convert `byte/rune array`(not only `slice`) to string.
2.convert string to string(itself), just like `string(str)` in go language.

Support for position independent executables (PIE) on the native linux
backend, the gdbserver backend on linux and the core backend.
Also implemented in the windows native backend, but it can't be tested
because go doesn't support PIE on windows yet.

This change adds a config flag to specify the foreground color of
line numbers for the source list command.

Use the defination of Server interface in service package, instead of
temporary in func.

Replace the socket connection with an in-memory connection (created by net.Pipe) for non-headless uses of delve.
This is faster and more secure.

Fixes #1332

On macOS 10.14 Apple changed the command line tools so that system
headers now need to be manually installed.

Instead of adding one extra install step to the install procedure add a
build tag to allow compilation of delve without the native backend on
macOS. By default (i.e. when using `go get`) this is how delve will be
compiled on macOS, the make script is changed to enable compiling the
native backend if the required dependencies have been installed.

Insure that both configuration still build correctly on Travis CI and
change the documentation to describe how to compile the native backend
and that it isn't normally needed.

Fixes #1359

With this syntax users do not need to type the concrete type of an
interface variable to access its contents. This also sidesteps the
problem where the serialization of a type by go/printer is different
from the one used for debug_info type names.

Updates #1328

Use IsInternal and IsUser of Breakpoint, not duplicate code

We should print something when we exit from continue/next/step/stepout
even if we don't have a source file for the instruction that we are
stopped on.

This is mostly important on macOS where a SIGSEGV will cause 'continue'
to fail with a 'bad access' error (see #852) and the output can be
confusing.

Fixes #1244

Correctly locates the installed executable path for darwin

Go allows converting a single integer value to string, resulting in a
string containing a single unicode rune with the same code as the value
of the integer.
Allow the same conversion to happen.

Fixes #1322

Instead of failing on the first goroutine we can't read save the error
message and keep going.

Fixes a bug reported on the mailing list:
https://groups.google.com/d/msgid/delve-dev/3b3bfaa3-83d5-4676-b974-1fec40e5bf53%40googlegroups.com?utm_medium=email&utm_source=footer

This commit just add an new error when trying to change register
values for core files (output the same infomation).

format `whatis <expression>`

This changes make `dlv` support multifile specifically when dlv `debug`,
`trace` and `test`. Just like `dlv debug a.go b.go`. Corresponding to
`go build a.go b.go`.(a.go and b.go are  belong to `main` package).

Fix #984.

Refactors some code, adds a bunch of docstrings and just generally fixes
a bunch of linter complaints.

An interface with a children that has onlyAddr set to true was not
loaded due to the depth limit having been reached.

We were using our makefile not for the intended purpose of makefiles
but to multiplex a series of small scripts.
We can easily achieve the same result in a more reasonable programming
language and as a bonus we don't need to install a version of make on
windows anymore.
Additionally our test script had become fairly complicated and will
become even more complicated when testing of PIE buildmode is
introduced.
Allows the tests to run on Windows without having to install Mingw
(although we still want it installed so that we can run cgo tests on
Windows).

Fixes building when GOPATH isn't set.

Fixes #759