a modified version of Echelon9's fix for Mantis #2897 (heap corruption due to object indexes being too large for the object dock bitstring)

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9708 387891d4-d844-0410-90c0-e4c51a9137d3
remove an unused function, per Echelon9's detective work (Mantis #2900)

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9709 387891d4-d844-0410-90c0-e4c51a9137d3