bug#13569: 24.3.50; gdb-control-commands-regexp has a typo

[Richard Kim]

My suggested change may not be adequate.

The full name of the gdb command in question is "commands".
However gdb allows  any one of these partial spelling of the name:
"comm", "comma", "comman", and "command".

emacs-23 has no problem dealing with any of these partial names.

emacs-24, however, only accepts the full name "commands".
If emacs-24 were to allow all legal shorthands, then "commands" in the regexp
should be replaced with  something like "comm\\(a\\(n\\(ds?\\)?\\)?\\)?".
I hope there is a simpler way to express this.