Mods to make merge with viewer-release have less whitespace-only change and fix diffs between EEP and VR.

Fix broken matrix management code causing modelview mats to be used as tex anim mats
(do not depend on default matrix mode already being set).

Give the deferred terrain shader a name.

Make LLRender use the eMatrixMode enum instead of ints.

Fix distortion map rendering in deferred mode not including underwater fog effects.

Fix distortion map rendering not including post-deferred content at all.

Fix distortion map rendering not including anything but sky when camera is underwater.

Update sun_up_factor/sunmoon_glow_factor uniforms even when sun disc isn't in use.

SL-9973

MAINT-7548 MAINT-7560 use NvidiaOptimusEnablement globally exported var to signal desire to use high-performance graphics processor

libatmosphere integrated in indra/llrender/llatmosphere.cpp

Still working on runtime shaders to use libatmosphere precomputed atmospherics textures

These changes are only enabled if RenderNsightDebugSupport is true and eliminate use of
some OpenGL legacy functionality which is incompatible with nSight capture
(mostly glReadPixels and other fixed-function pipe rendering calls).

MAINT-6913 - (Via Sovereign Engineer and Shyotl Kuhr) Pack the skinned matrix and translation into a single mat3x4 for optimal data transfer to reduce uniform slot usage.

replace llinfos, lldebugs, etc with new LL_INFOS(), LL_DEBUGS(), etc.

Reviewed by Graham

Reviewed by Graham