BGE: Fix for [#35479] "OSKEY (Command Key on Mac) not working" reported by Mike Pan (mpan3).

The OSKEY was never added to the game engine, so it didn't recognize it.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57593 954f8c5b-7b00-dc11-b283-0030488c597c