Check and use GL_ARB_texture_non_power_of_two and use it if present to allow using all textures unscaled. This makes a huge visual improvement since most skins are not power-of-two textures.
Conflicts:
src/client/refresh/header/local.h
MSAA was a long wanted and often requested feature. Just set set the
desired number of samples with gl_msaa_samples and do a vid_restart.
This code is based upon work done in Hecatomb.
Those extensions have become part of ARB about 15 years ago and most if
not all video cards still in use should support the ARB versions. I
believe that at least parts of this code were disfunctional.
This removes the need to define the old qgl function names to the
official OpenGL names. The OpenGL functions are now called directly
without any abstraction.
