fix Echelon9's fix >:(
also add a judicious Assert for Mantis #2958

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@10139 387891d4-d844-0410-90c0-e4c51a9137d3
fix an off-by-one error

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@10140 387891d4-d844-0410-90c0-e4c51a9137d3
re-commit r10082, except for ship.h, because it's the size of the ship_weapon struct that's causing the mysterious crashes (Mantis #2958)

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@10141 387891d4-d844-0410-90c0-e4c51a9137d3