Allow fixed linking to LIBGL/LIBAL.

Also check that all core functions are present when doing dynamic
linking to improve robustness.
Convert HQx and scrap to 32-bit color.

Allow putting small 32-bit pics onto the scrap and upscaling them.
Also limit upscaling level based on maximum GL rexture size.
Fix vwep model replacements.

Never try ‘male’ replacements for models other than ‘cyborg’. Custom
models depend on this original Quake 2 client behavior.