This is done with small adjustments to TextureFunctionHLSL. Most of
the functionality was already in place before.

This changes the categorization of sampler types in BasicTypes.h
helper functions: 2D array samplers are no longer treated as 2D
samplers, but the two categories are now entirely disjoint. This
makes TextureFunctionHLSL a little bit simpler.

BUG=angleproject:2775
TEST=angle_unittests, angle_end2end_tests

Change-Id: I84d9b56c37b1aaa01ee5921b6f17f8a78698fce2
Reviewed-on: https://chromium-review.googlesource.com/1188562Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>