Two small Lua documentation fixes.

git-svn-id: svn://svn.icculus.org/fs2open@10347 387891d4-d844-0410-90c0-e4c51a9137d3
Another little Lua documentation fix.

git-svn-id: svn://svn.icculus.org/fs2open@10348 387891d4-d844-0410-90c0-e4c51a9137d3