mesa,gallium: changes to allow reporting GL buffer size and compute limits up to 4G - 1 for glGetInteger64
This allows increasing UBO and SSBO limits up to 4GB - 1 while keeping the limit on GLSL uniforms low (i.e. not astronomical).
TBOs need more changes to be able to report 4G - 1 texels.
Only glGetInteger64 returns more than 2G - 1.