Previously, 'ldflags' were added to the compiler invocation based on the
version of Go the user was running. It seems to make more sense to
simply always pass along the flags on Darwin (due to the bug mentioned
in the comment above this line in the diff) as that is less brittle than
branching on the Go version, and yet will not break current users /
developers work flow.

Use proc.(*Process).FindGoroutine in proc.(*Process).SwitchGoroutine and
debugger.(*Debugger).Stacktrace. That method did not exist when those
were originally written.

Be more tolerant of unitialized memory, limit length of strings like we
do for array/slices.

Workaround for Issue #189

Replace function with a stdlib implementation.

Default numeric argument now simply represents the depth. If you would
like to see the stack trace of another goroutine, use `goroutine <id> bt`.

stack command: -full flag prints local variables and arguments of all the functions on the stack trace

Some of the goroutines stored in runtime.allg are in the dead state and
should not be displayed. The state is determined by the 'g.atomicstatus'
member.

The GoroutineInfo method can be slow if there are many goroutines. This
patch caches the results during a halt so they are not needlessly
recomputed.

Fixes #234

Updated doc with standard commit message format.

gopc is the instruction of the `go` command that spawned this goroutine.
What we really want (unless we can get the PC from the thread) is the
value of sched.pc which is the value of the PC at the time it was
parked.

`next` would hang in highly parallel programs, causing test flickers and
unexpected behavior. This patch fixes it by examining all stopped
threads whenever Delve gets a notification, instead of just the thread
that caused the stop.

This change right-aligns the register names in the output of the "regs" command,
and pads out the display of the hex value of each register to 16 bytes. This
makes scanning registers for set values a bit easier.

Support multiple file / directory tables for multiple compilation units.

- added a type DebugLines that can hold number of DebugLineInfo
- added a supporting attribute to DebugLineInfo called 'Lookup' which is to be
used to quickly lookup if file exists in FileNames slice
- added supporting methods to lookup and return corresponding DebugLineInfo
- changed the debug_line parsing behavior to read all the available tables and
push them to DebugLines

- since Process.lineInfo is now a slice, it was breaking AllPCsBetween as well
- updated that function's definition to accept a new filename parameter to be
able to extract related DebugLineInfo
- updated calls to AllPCsBetween

- fixed tests that were broken due to attribute type change in Process
- updated _fixtures/cgotest program to include stdio.h, so that it updates
.debug_line header
- added a test to check 'next' in a cgo binary
- OSX - 1.4 does not support cgo, handle that in new testcase

This patch forces Delve to be more mindful of how it handles many
threads and the goroutine context switching that occurs in such cases.

Bring similar code up to top level, and keep OS dependant code in OS
dependant files. DRY up code a bit.

This patch aims to improve how Delve tracks the current goroutine,
especially in very highly parallel programs. The main spirit of this
patch is to ensure that even in situations where the goroutine we care
about is not executing (common for len(g) > len(m)) we still end up back
on that goroutine as a result of executing the 'next' command.

We accomplish this by tracking our original goroutine id, and any time a
breakpoint is hit or a threads stops, we examine the stopped threads and
see if any are executing the goroutine we care about. If not, we set
'next' breakpoint for them again and continue them. This is done so that
one of those threads can eventually pick up the goroutine we care about
and begin executing it again.

Added subcommand which takes a path to an existing binary, starts it,
and begins a debug session.

The shortening of file paths is purely a terminal UI concern. Move that
code to the presentation layer, and remove from the service layer.