Separate function info from TIntermAggregate This change will make it easier to split types of TIntermAggregate nodes representing functions and function calls into different node classes. BUG=angleproject:1490 TEST=angle_unittests Change-Id: I730aa7858fe31fda86218fc685980c6ad486f5e0 Reviewed-on: https://chromium-review.googlesource.com/394706 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>