patch to use target specific .gdbinit file

[Kris Warkentin]

>
> Er, that is a single gdb executable supporting ``multiple architectures''.
>

Well then a configure option isn't the answer.  We build GDBs targetting 5
different CPUs.  At the moment, these are separate binaries so it's an easy
matter to have each binary look for a hard-wired $HOME/.gdbinit-nto<CPU>.
Someday, however, we want to multi-arch gdb (as we already have with
binutils) so that we can ship one gdb binary.  That is where the
configure/compile time setting of the extra gdbinit file falls apart.  What
I was asking about earlier was a runtime method of determining the file to
source so that if I use the same binary for multiple targets, I can source a
different file for each one.

I was thinking that we should put a hook in the code that is run when
switching targets to source a target file based on what gdb thinks its
target is at the time.

cheers,

Kris