Make sure that "scalar %= vector" is not approved by the compiler, and
that % and %= are only exposed on GLES3.

BUG=angle:854

Change-Id: I3ac7eb607bd86a6caa905d2bef5d397688ad3fd3
Reviewed-on: https://chromium-review.googlesource.com/241410Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Gregoire Payen de La Garanderie <Gregory.Payen@imgtec.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>