Remove some unused atmospherics helpers and forward declarations of unused helper funcs.

...settings/shaders/class1/deferred/avatarAlphaNoColorV.glsl

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

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

...ttings/shaders/class1/windlight/atmosphericsHelpersF.glsl

...ttings/shaders/class1/windlight/atmosphericsHelpersV.glsl

...ttings/shaders/class2/windlight/atmosphericsHelpersF.glsl

...ttings/shaders/class2/windlight/atmosphericsHelpersV.glsl

...view/app_settings/shaders/class3/lighting/sumLightsV.glsl