SL-17451 Fix for erroneous attempt to apply vertex color alpha to texture before alpha masking (we don't actually support this and the vertex color alpha is sometimes zero when you think it ought not be).

SL-17194 Impostor quality pass 2 (and fix for fully transparent rigged attachments rendering to depth buffer)

SL-17028 Fix for inconsistent ordering of transparent rigged meshes and removal of glow-only rigged meshes from depth buffer.

SL-16468 Fix for crash when enabling highlight transparent (add rigged mesh support to highlight transparent).

SL-14732: Merge Sovereign Engineer's cloud patch: Fix writing outside outside of the bound fbo in forward render class2 cloud shader

SL-14731: Fix sun gamma -- merge Sovereign Engineer's patch: Fix sun gamma space for accurate color reproduction of sun textures

Contribution

Removed some potential div-by-0 NaNs and a mangled clamp.

Had to find a balance in the sunlight intensity calculation that behaves correctly for
both these issues.