function support and a no-frills About box

Created macosx_common.h in plugins/macosx/ to hold , well, common stuff
(the way I see it, there is inherently a difficult separation of intf and
vout on Mac OS, if anyone has suggestions I'm open)

Cleaned up debug spew I left in modules.c and video_text.c

Hacked main.c to disregard argv[1] when compiled for OSX & run as a full
app (ie., double clicked and not launched from command line)... read the
file for more details.  UGLY.

Updated Makefile.in to make vlc.app by default on Mac OS X & Darwin, added
clean code for it as well