Fix mantis 2651: from ZekeSulastin

Add support for up to 98 joystick buttons

git-svn-id: svn://svn.icculus.org/fs2open@10933 387891d4-d844-0410-90c0-e4c51a9137d3
Trunk sync r10933.

git-svn-id: svn://svn.icculus.org/fs2open@10934 387891d4-d844-0410-90c0-e4c51a9137d3