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).

Add directory names to sentinels in shaders so shaders with same filename can be differentiated in nSight while debugging.

NORSPEC-57, NORSPEC-58  Remove sRGB and gamma correction from shaders to remove banding and not break all shiny objects.

SH-2908 Rework indexed texture rendering to use a uvec4 instead of a float for texture indices in the data stream.  Also rework gl_FragColor overrides to not collide with some odd driver implementations.

SH-2541 Fix for speckles on avatar on some cards -- don't use "maximum_alpha" for alpha tests in shaders as it was always being set to 1.0 anyway.

SH-2507 Potential fix for basic shaders causing objects to disappear with some drivers (prune shader tree of unused shaders while we're at it)

SH-2507 Potential fix for basic shaders causing objects to disappear with some drivers (prune shader tree of unused shaders while we're at it)

SH-2243 work in progress -- don't use gl_FragColor or gl_FragData for outputs -- no more deprecation warnings on nvidia

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