libRGL.so is now explicitely linked with libGLU.a and libGL.a. There is no

need anymore for macro GL.C (which was only implemented for linux anyway).
Everything works fine with the latest Mesa distribution v3.2.


git-svn-id: http://root.cern.ch/svn/root/trunk@111 27541ba8-7e3a-0410-8455-c3a389f83636