Fix opengl.py example on OS X
Fix opengl.py example on OS X

oktayacikalin/pyglet,theblacklion/pyglet,oktayacikalin/pyglet,theblacklion/pyglet,theblacklion/pyglet,oktayacikalin/pyglet,mammadori/pyglet,mammadori/pyglet,mammadori/pyglet,theblacklion/pyglet,mammadori/pyglet,oktayacikalin/pyglet,theblacklion/pyglet,oktayacikalin/pyglet