Update README.md

Confess neglect.
GL cleanup and gluErrorString removal

OSX 10.9 targets have deprecated glu/glut functions.  Remove the gluErrorString
dependency, and expose common GL routines previuosly excluded from GLES builds.
Fixed CMakeLists.txt bug for Ubunut 13.10 and Add handle fread error
code for fixed gcc -Wunused-result error