Fix section links in programming guide.
Fix section links in programming guide.

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