Fix CMakeLists.txt to work for ubuntu 13.04
Fix CMakeLists.txt to work for ubuntu 13.04

lanice/cg2sandbox,stephde/CG2Uebung,lanice/cg2sandbox,hpicgs/cg2sandbox,stiXits/demo_ray,lanice/cg2sandbox,stiXits/demo_ter,stiXits/demo_ter,stiXits/demo_ray,stiXits/demo_lod,stiXits/demo_ray,stephde/CG2Uebung,stiXits/demo_lod,hpicgs/cg2sandbox,stiXits/demo_ter,stiXits/demo_lod,stephde/CG2Uebung