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

SL-13084: Fix clouds flipped along East/West axis to match texture preview Cloud Image and direction to match Cloud Scroll

SL-13804: Fix clouds flipped along East/West axis to match texture preview Cloud Image and direction to match Cloud Scroll

SL-13084: Fix inverted cloud scroll with ALM is off

SL-13084: Move texture coords section to top in class2/windlight/cloudsV to match class1/deffered/cloudsV

SL-13084: Add references to other common files

Modify altitude blend factor in cloud shaders to fade more aggressively and fix cloud rendering artifacts when at altitude.

Fix class2/windlight clouds.

Use color channel for trees instead of shenanigans to get proper diffuse colors to shaders.

Remove fudge factors on density modifier in class1 sky.

Fix light atten and transmittance calcs breaking ambient color contrib to fog.

Needs to be tested on DRTSIM-415 or better to get legacy viewer settings that match EEP.

Re-fix sun/moon glow factor and make it depend on moon brightness.

Make cloud shaders use sunlight color exclusively for consistency when moon is up or down.

Gave clouds the Bob Ross treatment.

Fix direct light matching across alpha/blended-material/deferred.

Get diffuse lighting to match from Low to Ultra.

Remove all refs to now unused calcFragAtmospherics.

Fix skydome VB generation to cover entire range of phi (give sky pants).

Add shader code to fade out clouds to simulate old look at altitude.

Fix side-effects of having both sun and moon as potential directional light contributors.
We pass an int to the shader indicating which to prefer instead of making per-pixel decisions
and pass the moonlight color/di independently.

Obsolete llsettingssky fade color which was unused elsewhere and cached for no reason.

Fix bug with setting texture matrix for rigged mesh.

Fix z-fighting between sea and sky in ALM by cheating sky, stars, and moon using gl_FragDepth.

Fix handling of atmospheric haze glow w.r.t independent sun/moon positioning
(we can no longer depend on them being mutex to each other).

Fix positioning of sun/moon discs w.r.t atmo haze glow.

Disable killing glow when sun is not up.

SL-9851

Fix cloud shaders to ignore clouds when cloud_scale is 0.

Fix creation of heavenly body geo to avoid degenerate vector math
and not randomly flip orientation when crossing zenith.

Add sun_up_factor to eliminate sun glow around moon when sun is down.

EXP-2592 FIX -- (OS X Lion) Graphics issues with Atmospheric Shaders enabled on Intel HD 3000, 10.7.2

* Fixed up shaders to add haze_density and blue_density together correctly as vec4's rather than
  relying on the shader compiler to add them together properly.

SH-2592 PROGRESS -- (OS X Lion) Graphics issues with Atmospheric Shaders enabled on Intel HD 3000, 10.7.2

Refactored WindLight estate settings to use float uniforms in the shaders that
only need it, rather than vec4's for everything.

SH-1682 Dynamically adjust the number of texture channels to use for indexed texture rendering based on available hardware.

See https://wiki.lindenlab.com/wiki/License_Substitution for details.

windlight14 which have passed QA (up through r79932).

svn merge -r 80831:80833 svn+ssh://svn.lindenlab.com/svn/linden/branches/merge_windlight14_r80620