gdbstub initial code, v3

[Oleg Nesterov <oleg at redhat dot com>]

Please see the attached ugdb.c.

It supports multiple inferiors/threads, stop/cont, clone/exit.
It doesn't report W/X when the process exits yet, but this is
only because I'd like to discuss the current problems with the
exited leader first, then implement this as a separate change.

Any code review is very much appreciated.

Problems:

	- It doesn't support all-stop mode.

	  Please tell me if this is needed. I hope not, this needs
	  a lot of nasty complications :/

	- We should discuss utrace limitations: UTRACE_RESUME
	  races/problems, utrace_prepare_examine() issues.

	- I just finished this code, and it doesn't work with gdb ;)

	  I will investigate tomorrow, but I am almost sure gdb is
	  wrong.

Oleg.

Attachment: ugdb.c
Description: Text document