Fix a few mouse related issues.
This adds the CursorManager class which handles loading cursors and showing/hiding the cursor.

git-svn-id: svn://svn.icculus.org/fs2open@10487 387891d4-d844-0410-90c0-e4c51a9137d3
Adds cursor.h/.cpp to 2011 Project for building.

git-svn-id: svn://svn.icculus.org/fs2open@10488 387891d4-d844-0410-90c0-e4c51a9137d3