SL-19147 Water quality pass.  Remove gl_FragDepth writes from sky rendering (optimization).  Incidental decruft.

Modify sun disc shader to better position itself within the sun glow and to
fade as the sun approaches the horizon (to mask where the position difference is greatest).

Tweak position of sun in disc shader to better match the offset applied to the sun glow in atmospherics.

Make perspective projection consistent between ALM and non-ALM when drawing water (horizon matches).

Make perspective projection consistent between ALM and non-ALM when drawing heavenly bodies (sun disc position matches).

Make gamma correction of sun disc tex consistent between ALM and non-ALM rendering.

Make sun/moon vert shaders use calcAtmospherics in hopes it will get OSX GL to link the shaders without complaining about unwritten varying vars.

MAINT-8838 render a sun disc if the texture(s) are provided by WL settings (default is no sun disc and just haze)

Refactor sky texture optimization to retain building the cubemap used by shiny.

Make distinct ALM moon shader, tweak mix factor for day vs night moon shading, and fix transposed name of daycycle func.

Add MouseMoon positioning ala MouseSun debug setting and accessors to use it.

SH-2242 Physics shape display works again, added asserts to flush out areas where state being consumed by a shader does not match state being provided by vertex buffers.

SH-2031 High risk changeset, but potentially high reward.  Addresses frame stalls in renderer by never using the fixed function pipeline if shaders are available.

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.

Self reviewed.

Merge of QAR-1267 to trunk.  This was a combo merge of QAR-1175 (maint-render-9) and QAR-1236 (dll-msvcrt-2)

svn merge -r 109838:112264 svn+ssh://svn.lindenlab.com/svn/linden/branches/maint-render/maint-render-9-merge-r109833

QAR-389