Fold top-level `setq's and `define-key's into their corresponding defvar.

Fold top-level `setq's and `define-key's into their corresponding defvar.
(gdb-inferior-io-mode-map): New var.
Add bindings to it rather than to comint-mode-map.
(gdb-display-number-end): Use dolist.  Remove always-true test.
(gdb-delete-line): Move and simplify.
(gdb-display-end): Don't bother going to beg-of-line since we're there.
(gdb-array-format1): Use dolist.
(gdb-make-windows-menu, gdb-make-frames-menu):
Move to top-level code.  Move the menus to within the GUD menu.
Make the menus only appear in gdba mode.