2.28.11: implement deferred warnings for allegro. Beef them up for CCL.
Many thanks to Duane Rettig for explanations on how to support Franz. lisp-action cleaned up some more for deferred-warnings. test-deferred-warnings beefed up. CCL still isn't fully there yet, and needs to better detect forward reference to macros. Also, make safe-file-write-date NIL robust independently of implementation.