Prefer defvar-keymap in some progmodes

Prefer defvar-keymap in some progmodes

* lisp/progmodes/asm-mode.el (asm-mode-map):
* lisp/progmodes/bug-reference.el (bug-reference-map):
* lisp/progmodes/erts-mode.el (erts-mode-map):
* lisp/progmodes/flymake.el (flymake-mode-map)
(flymake-diagnostics-buffer-mode-map):
* lisp/progmodes/icon.el (icon-mode-map):
* lisp/progmodes/js.el (js-mode-map):
* lisp/progmodes/m4-mode.el (m4-mode-map):
* lisp/progmodes/mixal-mode.el (mixal-mode-map):
* lisp/progmodes/scheme.el (scheme-mode-map): Prefer defvar-keymap.