Assorted shader cleanup to remove a few warnings and errors for OS X.

...p_settings/shaders/class1/deferred/attachmentShadowV.glsl

...w/app_settings/shaders/class1/deferred/avatarShadowV.glsl

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

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

...w/app_settings/shaders/class2/deferred/sunLightSSAOF.glsl

...a/newview/app_settings/shaders/class2/windlight/skyV.glsl