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.
-Changed the transform matrix uniform to a 3x4 matrix and packed translation into it to free up uniforms. (3x3 is converted to 3x4 internally, so we were needlessly eating 3*52 extra uniform slots. translationPalette might also have been treated as a vec4 internally too, wasting 52 more slots.)
-matrix3x4 requires opengl2.1 and newer, so added a new featuretable mask.
-Also added a featuretable mask to disable hardware skinning and deferred shading on hardware with less than 1024 vertex uniforms.
NOTE: On old old old amd hardware, evidently a 3x4 matrix might be upgraded to 4x4. I'm unsure, but I doubt such hardware has 1024+ uniform components available to begin with. 4x3 supposedly doesn't do this, but opengl is column-major, so this makes little sense.
-Nametag bubble visbility is oddly inconsistent. May vanish with future planned UI merges...
-VBOs are PAINFULLY slow on ATI hardware. This repos self-compiled davep/shining-fixes branch, so I'll leave the ball in LL's court for now regarding that.
