RFA: add testsuite function for answering internal error questions

[Jim Blandy]

I've committed this.

Jim Blandy <jimb@redhat.com> writes:

> [re-posting: bad changelog entry.]
> 
> 2002-11-06  Jim Blandy  <jimb@redhat.com>
> 
> 	* lib/gdb.exp (gdb_internal_error_regexp): New variable.
> 	(gdb_internal_error_resync): New procedure.
>         (gdb_test): If the command results in an internal error,
>         answer GDB's questions until we get back to a prompt.