Allow Uint16Arrays uploads for texture_half_float
Specify reading from missing attachments

readPixels/copyTexImage2D/copyTexSubImage2D should generate INVALID_OP when reading from a missing attachment.
Changed oes-texture-float-and-half-float-linear tests to allow failure during glGenerateMipmap. This addresses https://github.com/KhronosGroup/WebGL/issues/408 .
Add test for EXT_srgb.
Corrections to PVRTC extension spec and conformance test
Removed spec update
Merge pull request #527 from toji/pvrtc_fix

Corrections to PVRTC extension spec and conformance test
Merge pull request #571 from jdashg/add-srgb-test

Add test for EXT_srgb.
Fixed bugs and used more WebGLTestUtils primitives in ext-sRGB.html test.

Verified on Firefox.
Merge pull request #595 from kenrussell/cleanup-srgb-test

Fixed bugs and used more WebGLTestUtils primitives in ext-sRGB.html test...
Merge pull request #526 from kenrussell/gen-mipmap-fp-texture

Changed oes-texture-float-and-half-float-linear tests to allow failure d...
Merge pull request #475 from jdashg/half-float-uploads

Allow Uint16Arrays uploads for texture_half_float
Expanded framebuffer-object-attachment test to verify the cases in pull request #479.
Merge pull request #479 from jdashg/read-missing-attach2

Specify reading from missing attachments
Merge pull request #596 from kenrussell/read-from-missing-framebuffer-attachments

Expanded framebuffer-object-attachment test to verify the cases in pull ...
Added clarification about reading from missing attachments to copyTexImage2D, copyTexSubImage2D, and readPixels.

Follow-on to pull request #479.
Merge pull request #597 from kenrussell/clarification-of-read-from-missing-fb-attachments

Added clarification about reading from missing attachments to copyTexIma...
Added getBufferSubData and removed enums related to MapBufferData.

Also updated last modified date and regenerated WebGL 2 IDL.

Addresses Issue #541.
Reformatted paragraph.
Merge pull request #598 from kenrussell/get-buffer-sub-data

Added getBufferSubData and removed enums related to MapBufferData.