Allow glXChooseFBConfig to return sRGB capable fbconfig

Mesa's glXChooseFBConfig will not return any sRGB capable fbconfig when it
is not explicitly asked for. On some systems, the only ARGB32 visual is
paired with an sRGB capable fbconfig, so application windows using ARGB32
visuals would fail to display.

BUG: 387159
FIXED-IN: 5.11.4