Don't explicitly set LIBGL_DRIVERS_PATH by default; breaks autodetection
Fix shader compilation/out-of-spec issues
Merge remote-tracking branch 'upstream/master'

Conflicts:
	indra/llrender/llshadermgr.cpp (resolved)
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'

Conflicts:
	indra/newview/app_settings/shaders/class1/deferred/alphaNonIndexedNoColorF.glsl
	indra/newview/app_settings/shaders/class1/deferred/fullbrightShinyF.glsl
	indra/newview/app_settings/shaders/class1/deferred/fxaaF.glsl
	indra/newview/app_settings/shaders/class1/deferred/giF.glsl
	indra/newview/app_settings/shaders/class1/deferred/multiSpotLightF.glsl
	indra/newview/app_settings/shaders/class1/deferred/softenLightF.glsl
	indra/newview/app_settings/shaders/class1/deferred/spotLightF.glsl
	indra/newview/app_settings/shaders/class2/deferred/alphaF.glsl
	indra/newview/app_settings/shaders/class2/deferred/alphaNonIndexedF.glsl
	indra/newview/app_settings/shaders/class2/deferred/alphaNonIndexedNoColorF.glsl
	indra/newview/app_settings/shaders/class2/deferred/multiSpotLightF.glsl
	indra/newview/app_settings/shaders/class2/deferred/spotLightF.glsl
Re-fix shader compilation errors
Merge https://github.com/abaph/SingularityViewer

Brings in support for MESA accelerators.
Sprinkle some Intel GPU support on Linux
Clean up shaders on package and no longer final-package by default on Linux