Add support for GL_NV_read_depth

Change-Id: If2f96b4cc1c09cd28771740f09be5f84875033ab
Reviewed-on: https://swiftshader-review.googlesource.com/5091
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
8 files changed