Commit 3fb6380 was supposed to increase MAX_TEXTURE_HOOKS but instead
increased SHADER_MAX_HOOKS, since I forgot that they were separate (for
whatever reason).
To prevent this mistake from happening again, and to unify the location
in which user_shader-specific #defines are placed, get rid of the two
constants in opengl/video.c and move/reuse them from user_shaders.h
instead.
Also bump up MAX_SAVED_TEXTURES (now SHADER_MAX_SAVED) slightly as a
precaution against adding more passes to vo_opengl. I think we're
already flirting with the limit.
0af561953a