C++: Extend alias declaration support in built-in parser

The type-id in an alias declaration can also define a new type.

Change-Id: I65dc397d2526c56334676c6ab522564f6748d594
Task-number: QTCREATORBUG-24875
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

tests/auto/cplusplus/cxx11/data/aliasDecl.1.cpp

@@ -2,3 +2,5 @@ using Foo = int;
 using Bar = std::vector<int>::value_type;
 using A [[foo]] = const float;
 using B alignas(void*) = C *;
+using C = struct {};
+using D = enum class E {A, B};