Precision qualification is now checked properly also for declarations
that don't have qualifiers.

BUG=angleproject:1574
TEST=angle_unittests

Change-Id: I3d186df0763e071614c1da9a355a6f6fefdc8091
Reviewed-on: https://chromium-review.googlesource.com/403949
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>