(gud-minor-mode): New var.

(gud-minor-mode): New var.
(gud-symbol, gud-val): New functions.
(gud-find-file): Copy gud-minor-mode to the new buffer.
(gud-menu-map): Include entries for commands that are not always
available, using :enable to (de)activate them.
(gud-minor-mode-map): New map.  Add it to minor-mode-map-alist.
(gud-mode-map): New map.
(gud-gdb-find-file, gud-sdb-find-file, gud-dbx-find-file)
(gud-xdb-find-file, gud-perldb-find-file, gud-pdb-find-file):
Don't set up gud's menu (it's done by the minor-mode).
(gud-minibuffer-local-map): New.
Replace gdb-minibuffer-local-map and pdb-minibuffer-local-map.
(gud-query-cmdline): New function.
(gdb, sdb, dbx, xdb, perldb, pdb, jdb): Use it.  Set gud-minor-mode.
(gud-mode): Use define-derived-mode.
Don't set up gud's menu (it's done by the minor-mode).
(gud-chop-words): Remove.
(gud-common-init): Use split-string instead.
(gud-new-keymap, gud-make-debug-menu): Eradicate.