Atomic counter arrays may be declared with various different syntax -
the array size may be declared as a part of the type or as a part of
the declarator. Take this into account when determining whether atomic
counter offsets overlap.

BUG=angleproject:1729
TEST=angle_unittests

Change-Id: I7435ded9401c4c1caab22c22d83fd2ad301df768
Reviewed-on: https://chromium-review.googlesource.com/738140Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>