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.

back-out the back-out for this branch.  yay.

Backing out this merge that I pushed (prematurely) to the wrong place.

kill already-nerfed quadratic attenuation which it seems we won't be supporting any decade soon.

kill already-nerfed quadratic attenuation which it seems we won't be supporting any decade soon.

kill already-nerfed quadratic attenuation which it seems we won't be supporting any decade soon.

cheaply resurrect the difference between spotlight and omnidirectional, as far as the shader is concerned.

not complete.

cheaply resurrect the difference between spotlight and omnidirectional, as far as the shader is concerned.

not complete.

cheaply resurrect the difference between spotlight and omnidirectional, as far as the shader is concerned.

not complete.

next, needs the non-shader GL lighting model to be equally dumb (it's too smart - kill the spot angle.

next, needs the non-shader GL lighting model to be equally dumb (it's too smart - kill the spot angle.

next, needs the non-shader GL lighting model to be equally dumb (it's too smart - kill the spot angle.