* lisp/progmodes/bat-mode.el (bat-font-lock-keywords): Fontify
argument numbers in %~n. Suggested by Jostein Kjønigsen
<jostein@secure.kjonigsen.net> in emacs-devel.
* test/lisp/progmodes/bat-mode-tests.el
(bat-test-fontification-iter-var-1): Update the test to check also
the %~n construct.