PhysX 3.3, building on linux

This updates the project to physx 3.3 and magically fixes linking errors on linux.
Links against static libraries on linux, that's why have have to link all the physx libraries there, even those we do not use.

Uses the "Checked" libraries by default, causing the program to crash where too many particles are created and the old ones are not deleted before. (Which caused console warnings before, see #68).

Also fixes some (terrain) rendering issues, that didn't occur with windows drivers.

Please check if it works on both platforms, and fix #68.