some gl header fixes/additions
remove dependecy on glew
tests/examples: remove dependency on glew
effects: fixes for mirror(1) and squeeze(2) producing black
filter: fix _draw_texture()'s wrong vertices
up/download: fix some typos when removing GLEW
bumper: port to non-GLEW + arrays
deinterlace: port to non-GLEW + arrays
differencematte: port to non-GLEW