here a const, there a const, everywhere a const const

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9801 387891d4-d844-0410-90c0-e4c51a9137d3
remove Bobboau's "better error messages" which were never fully implemented and are more distracting than helpful

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9802 387891d4-d844-0410-90c0-e4c51a9137d3