Add support for C++'s "type-specifier ( expression-list )" expression:

Add support for C++'s "type-specifier ( expression-list )" expression:

-The Parser calls a new "ActOnCXXTypeConstructExpr" action.
-Sema, depending on the type and expressions number:
   -If the type is a class, it will treat it as a class constructor. [TODO]
   -If there's only one expression (i.e. "int(0.5)" ), creates a new "CXXFunctionalCastExpr" Expr node
   -If there are no expressions (i.e "int()" ), creates a new "CXXZeroInitValueExpr" Expr node.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@55177 91177308-0d34-0410-b5e6-96231b3b80d8