Minor enhancements to Emacs packages

[Ziemowit Laski]

Hi,

I've made small enhancements to three packages (mouse.el, menu-bar.el and
gud.el) that ship with GNU Emacs and was wondering whom I should send them to
and in which format (old + new, just diffs, etc.).

Here's a brief description:

mouse.el/menu-bar.el: I've added a defcustom variable that allows disabling
copy-yank-as-kill for text selected with the mouse (the user must cut/copy
explicitly, like on MacOS or Windows).

gud.el: I've added a defcustom variable that controls if, when a debugging
session is launched, the current directory is switched to that of the
executable being debugged; also, the command name for gdb (plus any
parameters) may now be specified in another defcustom var.

Both changes have "polite" defaults which replicate previous behavior.

Please let me know if these would be of interest to the Emacs project.
Thanks,

Zem Laski