Split TIntermFunctionPrototype from TIntermAggregate Function prototypes now have their own class TIntermFunctionPrototype. It's only used for prototypes, not function parameter lists. TIntermAggregate is still used for parameter lists and function calls. BUGS=angleproject:1490 TEST=angle_unittests Change-Id: I6e246ad00a29c2335bd2ab7f61cf73fe463b74bb Reviewed-on: https://chromium-review.googlesource.com/427944 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>