gdbstub initial code

[Roland McGrath]

> Note that currently I am not even trying to do something meaningful
> with utrace. My only goal for now is to implement the very basic things
> like attach/detach/stop/cont/exit correctly from the remote protocol
> pov. And I want to do this "rightly", then we will discuss utrace
> issues.

Ok.  I think you might need select to work on the pseudofile for gdb to be
happy.  I'm not sure on the situation about that.


Thanks,
Roland