Image thread doesn't need mBuffer and buffer isn't thread safe so no point allocating it in an image thread.

SL-16418 Media texture update stall fix.  Make media texture updates use LLImageGL thread to update, fix AMD sync issue on ImageGL thread and install debug callbacks on LLImageGL thread when debug gl enabled.

SL-16653 Fix for some textures having incorrect texel colors after the first row (and add more paranoia checks on texture data).

remove unused variable

SL-16166 Apply optimizations from pushBatch to other render call sites.  Optimize out a map lookup in rigged face rendering.

SL-16093 Don't force the console window to be open on developer builds because it causes frame stalls while logging.