Merge branch 'master' into rend2
[MP] Rend2: Variety of changes/improvements

* Removed alternative specular lighting models. Only GGX remains now.
* Added support for HDR cubemaps.
* Ghoul2 models now use cubemaps for IBL.
* Changed default r_baseGloss to 0.1 (was 0.3)
* Changed default r_dlightMode to 1 (was 0)
[MP] Rend2: Selectively picked changes from ioq3

This commit selectively picks changes from ioq3's rend2 regarding cubemap
normalization which wasn't necessary.
Merge remote-tracking branch 'upstream/rend2' into rend2