The new class TIntermDeclaration is now used for struct, interface
block and variable declarations. TIntermDeclaration nodes do not have
a type - rather the type is stored in each child node. The types may
differ in case the declaration is a series of array declarators with
mismatching sizes.

TIntermAggregate is still used for function calls, function
prototypes, function parameter lists and invariant declarations.

BUG=angleproject:1490
TEST=angle_unittests

Change-Id: I0457188f354481470855f61ac1c878fc2579b1d1
Reviewed-on: https://chromium-review.googlesource.com/400023
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>