Fix framebuffer completeness tests with sRGB targets.

- Don't expect SRGB to become renderable in GL_EXT_sRGB extension
- Support GL_EXT_sRGB_write_control extension
- Support GL_NV_sRGB_formats extension
- Add missing GLES3 texture formats
- Remove modified cases from must-pass list

Bug: 18094134
Change-Id: I7587ff4a0e6106b74780dae193fa16970145a02e
6 files changed