-var-update using formatted value

[Marc Khouzam]

> You can see what Emacs 22.1 does quite easily.  You probably don't want to look
> through thousands of lines of lisp code (gdb-ui.el) but you can just set
> gdb-enable-debug to t and look at the value of gdb-debug-log after issuing some
> commands to GDB in a session in Emacs (M-x gdb) so see the transactions.

I downloaded emacs 22.1 a gave it a spin.  It's pretty cool, the new GUI for GDB.
But I don't know how to set gdb-enable-debug to t or to look at gdb-debug-log after.
My emacs is pretty darn rusty.
I also couldn't figure out how to change the format to hex for a watch expression.

I did have a look at gdb-ui.el and I saw pretty much every -var-command used but 
I could not find any reference to -var-set-format...

> In fact, I'd be interested to know how well (badly?) GDB in Emacs performs
> in an embedded environment.

I currently don't have a setup to properly test this, but it is something we
will be eventually looking into.  At that time, I can give emacs a try.

Marc