assert instead of throwing an exception when an invalid gl call happens so we get the stack trace.
assert instead of throwing an exception when an invalid gl call happens so we get the stack trace.

svn path=/trunk/libavg/; revision=5398

libavg/libavg,hoodie/libavg,libavg/libavg,libavg/libavg,th3infinity/libavg,hoodie/libavg,th3infinity/libavg,scotty007/libavg,yyd01245/libavg,th3infinity/libavg,yyd01245/libavg,yyd01245/libavg,hoodie/libavg,scotty007/libavg,scotty007/libavg,libavg/libavg,yyd01245/libavg,th3infinity/libavg,scotty007/libavg,hoodie/libavg