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
Allow calling LLNotificationsUtil::add from any thread.

This makes LLStringUtil thread-safe by removing a rather unnecessary
LLFastTimer from LLStringUtil::format.

Same thing for LLTrans::getString and LLTrans::findString, where
even a comment stated that the author wasn't interested in measuring
cpu time at all. In this case I added some code back to make sure
that we're not calling LLTrans::getString() in an inner loop, which
was the reason that the LLFastTimer was added.

Made one string static to avoid 45000 look ups during login, which
kinda triggered the above test.

Finally, LLNotificationsUtil::add is made thread-safe by making
LLNotificationChannelBase::mItems thread-safe and defering a call
to LLNotifications::updateItem to the main thread when called
from another thread (using a little statemachine).
Merge remote-tracking branch 'singu/master'
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
Initialize LLListener_OpenAL::mRolloffFactor just to be safe.
Font update. Minor refactor, and removed some pointless code that was leaking.
Underwater shadows.
Removed fasttimer that was hurting perf a tiny bit.
Merge branch 'master' of https://github.com/singularity-viewer/SingularityViewer.git