SL-18190 WIP - Linear space atmospherics take 2

...ew/app_settings/shaders/class1/deferred/deferredUtil.glsl

...wview/app_settings/shaders/class2/deferred/pbralphaF.glsl

.../app_settings/shaders/class2/windlight/atmosphericsF.glsl

..._settings/shaders/class2/windlight/atmosphericsFuncs.glsl

...pp_settings/shaders/class3/deferred/reflectionProbeF.glsl

...ew/app_settings/shaders/class3/deferred/softenLightF.glsl

indra/newview/llreflectionmap.cpp