fixes issue #179

For more information see: https://github.com/golang/go/issues/11887

the entry point of a function is the beginning of the prologue, which can be run multiple times for each invocation of a function if the stack needs to be expanded or the scheduler needs to be run.

The process will already be killed via withTestProcess

proc.(*Thread).GetG: reading TLS memory directly for g address instead of modifying the executable code

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

bugfix: rpc.(*RPCClient).AttachedToExistingProcess calling the wrong function, this would result in the terminal frontend always killing a process it was attached to

This makes parsing by external tools much easier.
It is consistent with pdb.

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

Also, reorganizes some code.

Initially, the `proc` package emitted a lot of output. Now, that should
not be the case. The `proc` package should never print, for any reason.
That should be handled by clients.