Reviewed by Graham

Reviewed by Graham

Performance improvements. Faster threadsaferefcount, faster instancetracker, use hashtable and pre-hashed strings for GLSL uniform lookup, and use dup_handles curl interface to avoid re-initing ares resolvers expensively.

For MAINT-2003 and MAINT-1555 Fixes sequencing issue in determining max vram where mem multiplier was being done after already clamping to 512M, robbing people with >512M of 256M. Code review: DaveP

For MAINT-2003 Fix sequencing issue causing mem multiplier to be applied after clamping below actual mem available

Reviewed by Graham

reviewed with Simon

For MAINT-755 Fix for unbinding cubemap causing false alarm in tex type checking code (OS X RenderDebugGL crash) Code review: Dav3p

MAINT-2390 Fix for texture animation corrupting face repeats on rigged attachments after switching off animation.

MAINT-2370 Add debug setting "RenderAutoMuteRenderCostLimit" that automatically visually mutes avatars above a certain threshold (adjusted by Avatar Mesh Detail Slider)

For MAINT-1291  Re-order cubemap disable and shader tex disable to avoid false alarm when using RenderDebugGL. Code Review: DaveP