Fix 2 for mantis 2901: 7 weapon slots (not 12) for pilot conversions

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9745 387891d4-d844-0410-90c0-e4c51a9137d3
Fix 3 for 2901: remove long/short read warning by making mainhall(csg flags), cutscenes(csg flags) & is_multi(plr flags) consistent between pilot conversion and normal save/loads

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9746 387891d4-d844-0410-90c0-e4c51a9137d3