Adding some GLES 3.0 specific enums

Adding some GLES 3.0 specific enums

This cl doesn't actually do anything, but we need to establish
exactly how to add new GLES 3.0 specific cases in Swift Shader.

Change-Id: I7f31ea98e0d24f71204a3e1a7a31bf3379741e15
Reviewed-on: https://swiftshader-review.googlesource.com/2560
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>