Convert some progmodes menus to easy-menu-define

Convert some progmodes menus to easy-menu-define

* lisp/progmodes/asm-mode.el (asm-mode-map):
* lisp/progmodes/grep.el (grep-mode-map):
* lisp/progmodes/m4-mode.el (m4-mode-map):
* lisp/progmodes/sh-script.el (sh-mode-map): Move menu definition from here...
* lisp/progmodes/asm-mode.el (asm-mode-menu):
* lisp/progmodes/grep.el (grep-menu-map):
* lisp/progmodes/m4-mode.el (m4-mode-menu):
* lisp/progmodes/sh-script.el (sh-mode-menu): ...to here, and rewrite
using easy-menu-define.