Prevented $On Action hooks from being executed more than once per frame.

git-svn-id: svn://svn.icculus.org/fs2open/branches/zookeeper@9836 387891d4-d844-0410-90c0-e4c51a9137d3
Upped the hook condition length limit from 32 to 128 and moved the limit to its own define.

git-svn-id: svn://svn.icculus.org/fs2open/branches/zookeeper@9837 387891d4-d844-0410-90c0-e4c51a9137d3
Slightly streamlined the code for the $Action hook condition.

git-svn-id: svn://svn.icculus.org/fs2open/branches/zookeeper@9838 387891d4-d844-0410-90c0-e4c51a9137d3