Add preprocessor macro for MeshLodGenerator build.
Add preprocessor macro for MeshLodGenerator build.

--HG--
branch : ogre-gsoc2013-progressive-mesh-improvements

jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre