[MP] Merged fix from ioq3 that was reported by me: ioquake/ioq3@983ebbb
Ignore -psn* arguments on Mac OS X
Mac OS X adds an argument starting with "-psn" when launched using Finder, Dock,
or a terminal using open command and not specifying arguments.

It caused the opening videos to be skipped.

This change mimics SDL 1.2.