macosx_finder_args: add SDL specific code path
SDL bootstrap code (include SDL.h in mplayer.c) creates its own minimal
Cocoa Application and creates a new argv to abstract away OSX specific
stuff (like -psn). For this reason the original code was not entering the
correct code path. This resulted in mplayer2 spamming to system.log.
Add a different code path to handle the case where SDL boostrap code ran.
Also, sort the files by filename for both SDL and no-SDL code paths: when
files are double clicked or drag and dropped to the mplayer2 icon they can
be in random order. Opening them with command + down arrow already
worked correctly.