Patch https://go-review.googlesource.com/23085 has been merged so we
can go back to using golang.org/x/debug/.

See: https://github.com/golang/go/issues/16180

This provides a better error message when the user tries to run dlv
debug on a directory that does not contain a main package, when `dlv
exec` is used with a source file.

Additionally the architecture of the executable is checked as suggested
by @alexbrainman in #443.

Fixes #509

* tests: update to cope with go1.7 SSA compiler

* de-vendored golang.org/x/debug/dwarf

We need our own tweaked version

* dwarf/debug/dwarf: always use the entry's name attribute

Using the name attribute leads to better type names as well as fixes
inconsistencies between 1.5, 1.6 and 1.7.

* proc: Updated loadInterface to work with go1.7

go1.7 changed the internal representation of types, removing the string
field from runtime._type.
Updated loadInterface to use the new str field.

* proc: add tests for command-line arguments

adds tests to make sure command-line arguments are passed to Launch() properly

* proc_windows: pass command-line arguments to CreateProcess()

build command-line arguments according to how the standard library does it and pass the command line along to the actual syscall on Windows.

see discussion in #479

* proc: better testing of cmd-line arguments

* proc_windows: fix a possible error-case with passing just 1 argument

previously, the command line pointer passed to sys.CreateProcess was empty, if we had 0 parameters (len(cmd) == 1, as cmd[0] is the executable, so no cmdlineGo would be created, while with any argument it would as len(cmd) > 1). This might cause problems down the road, so make sure we include the command line every time, even if it seems to work without.

* proc: improve testing of command-line arguments

test that arguments with spaces are passed on correctly and DRY failure/success condition checking in the args test

Unrelated to conversion, I have also changed (*Thread).readMemory
to return only first count bytes of memory just as advised
by ReadProcessMemory.

Fixes #409
Fixes #412
Fixes #416

Fixes #398.

This patch modifies the `step` command to step to the next source line,
stepping into any function encountered along the way.

Fixes #360

Typedefs that resolve to slices are not recorded in DWARF as typedefs
but instead as structs in a way that there is no way to know they
are really slices using debug/dwarf.
Using golang.org/x/debug/dwarf instead this problem is solved and
as a bonus some types are printed with a nicer names: (struct string
→ string, struct []int → []int, etc)

 Fixes #356 and #293

Fixes #198.