Add support for new ESSL 3.00 keywords.

Bug 19331817

Change-Id: I3315de44d1976219fada3013af13146433aa6eaa
Reviewed-on: https://swiftshader-review.googlesource.com/2100
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>