Use font-lock-ensure when available.

font-lock-fontify-buffer is for interactive use only in Emacs 24.5
and later.
Merge pull request #340 from Fanael/master

Change one accidentally omitted loop to cl-loop.
Merge pull request #341 from Fanael/font-lock-ensure

Use font-lock-ensure when available.
Remove unnecessary byte-compile-warnings file local variables.

Now that we no longer use (require 'cl), we don't want to turn any
warnings off.