Add varying packing test
Merge pull request #160 from greggman/add-varying-packing-test

Add varying packing test
Update shader uniform packing test to check vertex shaders.
Merge pull request #161 from greggman/add-vertex-shader-uniform-packing

Update shader uniform packing test to check vertex shaders.
Merge pull request #159 from pyalot/sRGB2draft2.0

moved EXT_sRGB from proposal to draft
moved ANGLE_instanced_arrays from proposal to draft