[AD] al_get_path_basename

["Trent Gamblin" <trent@xxxxxxxxxx>]

I find the name of this function a little confusing. When I read it I think
it should behave like the unix "basename" command, which returns the
filename part WITH extension. But the allegro function returns the
filename part without the extension.  I do think we should keep the
functionality but maybe consider a different name.


Trent :-)