Use m[n:] to skip the first n keys of a map
Map indexing is implemented with a linear scan

Implements #61, #122

Pretty print will print them with the format:
chan <element type> <queued elements>/<queue size>

Supported operators:

- All (binary and unary) operators between basic types except <-,
++ and -- (includes & to take the address of an expression)
- Comparison operators between supported compound types
- Typecast of integer constants into pointer types
- struct members
- indexing of arrays, slices and strings
- slicing of arrays, slices and strings
- pointer dereferencing
- true, false and nil constants

Implements #116, #117 and #251

The new contents of api.Variable are documented in
proc/variables.go.

Implements #243

Three locations are returned for goroutines: its current location,
its current location excluding unexported runtime functions and
the location of its go instruction.
The command 'goroutines' takes a new parameter to select which
location to print (defaulting to current location w/o runtime)

Embedded structs are encoded in DWARF as fields with
package-qualified names.  They define an anonymous field
on the struct with the non-qualified name, as well as
promoted fields for each field of the embedded struct so
long as these are not shadowed by fields of the containing
struct.

Fixes #220.

g.SP refers to the frame the goroutine was in the last time it was
scheduled out. Instead of calling proc.(*Process).stacktrace directly
we should call proc.(*Process).GoroutineStacktrace that substitutes
fresh values retrieved from thread registers when necessary.
This bug leads to occasional problems with `next`.

Fixes #220

set <variable name> <value>

Refactored variables.go to separate calculation of a variable's address from
reading its value. This change is useful to implement the 'set' command
as well as the evaluation of more complex expressions (in the future).

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

Workaround for Issue #189

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.

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.

This fix helps avoid infinite recursion.

Fixes #192

bugfix, Issue #163: offset of g struct in TLS picked based on the value of runtime.buildVersion and presence of compile units created by GNU AS, instead of being fixed to -16

Allows a user to execute `dlv trace [regexp]` and Delve will execute the
program and output information on functions matching [regexp].

Finishes #63 #64

* Remove half baked CallFn implementation.
* Cleanup whitespace
* Cleanup read/write mem functions

Process is an incorrect name for the DebuggedProcess struct that the
thread is "a part" of. Also, no need to export that field.