Add the toggle-subsystem-scanning option to the alter-ship-flag SEXP

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9759 387891d4-d844-0410-90c0-e4c51a9137d3
Add alter-ship-flag support for several more flags

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9760 387891d4-d844-0410-90c0-e4c51a9137d3