Revert 10149. Needs more review

git-svn-id: svn://svn.icculus.org/fs2open@10154 387891d4-d844-0410-90c0-e4c51a9137d3
Changed most MessageBox calls to use SCP_Messagebox, also fixed some of the event processing.

git-svn-id: svn://svn.icculus.org/fs2open@10155 387891d4-d844-0410-90c0-e4c51a9137d3
fix some things that FreeBSD complained about

git-svn-id: svn://svn.icculus.org/fs2open@10156 387891d4-d844-0410-90c0-e4c51a9137d3