Implement R5G6B5 to 4.12 normalization. Bug 20891368 Change-Id: I492a3420facefed5a0ff7e469da54fd67bd68092 Reviewed-on: https://swiftshader-review.googlesource.com/3115 Reviewed-by: Alexis Hétu <sugoi@google.com> Reviewed-by: Nicolas Capens <capn@google.com> Tested-by: Nicolas Capens <capn@google.com>