Underlying C++ model sometimes marks C++ object instantiation using initializer
as a (forward) function declaration. This leads to incorrect highlighting of
object variables as if they were function calls.

C++ model however marks in this case (and not any other case) such symbols as
ambiguous function types, see CPlusPlus::Bind::visit. This change skips such
ambiguous functions for highlighting as function call.

Also add test case for related bug report.

Task-number: QTCREATORBUG-15212
Change-Id: Ifde8db407f2fa8275a3f991bfa3d3b73eca8c14e
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>