Sync light state, bound shader, and various gl context states similarly to render matrices.
Texture handles now refcounted, as multiple viewer textures could ref the same handle (cubemaps do this)
Clean up gl extension loading a bit. Not necessary, but only look for ARB variants if not included in current core version. Removed unused extensions.
Use core shader api if supported, else use ARB. (FN signatures are identical. Just doing some pointer substitution to ARB if not core.)
Attempt at improving VBO update batching. Subdata updates better batched to gether per-frame.
There's probably other stuff I forgot that is in this changeset, too.
Todo: Fix lightstate assertion when toggling fullscreen with shaders off.
Deferred fastalpha behaves a bit better.
Pulled over patch for https://jira.secondlife.com/browse/STORM-336 and https://jira.secondlife.com/browse/STORM-1011 from linden repo
Sky rendered using new LL method. Assuming this fixes issues on AMD cards(works on cat 11.2)
Added a few things missed related to spatial-parition updating.
Added 'SkipReflectOcclusionUpdates' setting that prevents occlusion updates for reflection pass. Less taxing on CPU.
