Shader cleanup and consolidation of use of sRGB conversion funcs.

.../newview/app_settings/shaders/class1/deferred/alphaF.glsl

...iew/app_settings/shaders/class1/deferred/fullbrightF.glsl

...wview/app_settings/shaders/class1/deferred/impostorF.glsl

...wview/app_settings/shaders/class1/deferred/materialF.glsl

...app_settings/shaders/class1/deferred/multiSpotLightF.glsl

...ngs/shaders/class1/deferred/postDeferredGammaCorrect.glsl

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

...view/app_settings/shaders/class1/deferred/spotLightF.glsl

indra/newview/app_settings/shaders/class1/deferred/srgb.glsl

...iew/app_settings/shaders/class1/deferred/underWaterF.glsl

.../newview/app_settings/shaders/class1/deferred/waterF.glsl

...ewview/app_settings/shaders/class1/environment/srgbF.glsl

.../app_settings/shaders/class1/windlight/atmosphericsF.glsl

...app_settings/shaders/class2/deferred/multiSpotLightF.glsl

...ew/app_settings/shaders/class2/deferred/softenLightF.glsl

...ew/app_settings/shaders/class2/deferred/softenLightV.glsl

...view/app_settings/shaders/class2/deferred/spotLightF.glsl

...iew/app_settings/shaders/class3/windlight/transportF.glsl