Back to ugdb.

Changes: implement stepi, this also means breakpoints work too.

Notes:

	- almost untested, probably needs more fixes

	- syscall-stepping doesn't work correctly (should be simple)

	- don't look at handle_setregs/handle_set_one_reg, I did
	  this on purpose to be sure I really understand what gdb
	  actually does

Well. This wasn't simple because I nearly got heart attack twice
when I was writing this change ;)

However, it turns out that ptrace-utrace (old or recently changed)
is innocent.

I found 2 problems, the 1st one is /usr/bin/gdb bug, another one
(I believe) is utrace core bug. I'll report tomorrow.

Oleg.