Upgrade LWJGL to 2.9.0, fixing Issue #643

I upgraded LWJGL to 2.9.0, fixing Issue #643, which apparently only occurs on Mac. I have absolutely no idea on the implications of this change, so to all you experienced Terasology folks, please help me out here :smile: 

What I can say is that this change, together with #642, made Terasology run on OS X 10.8, and there weren't any obvious bugs (that is, I ran around for a while and nothing seemed wrong or broken).