Accept equality and assignment for arrays in parsing This is enough to support the operations in GLSL output. HLSL output will likely require additional work to support this. BUG=angleproject:941 Change-Id: I728d511ab07af94bc3382dc2796c1e9ac79d1442 Reviewed-on: https://chromium-review.googlesource.com/260801 Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Olli Etuaho <oetuaho@nvidia.com>