CppTools: Add basic completion support for qt5 style signals/slots

Trigger completion for Qt5 signals/slots as soon as the user types '&'
in

    connect(object, &
    connect(object, &Foo:signal, object2, &

Change-Id: I338a26415196959e3dc413bdfd023314812f3aaa
Reviewed-by: Erik Verbruggen <erik.verbruggen@theqtcompany.com>

src/plugins/cpptools/cppcompletionassistprovider.h

@@ -65,7 +65,7 @@ public:
 
     static int activationSequenceChar(const QChar &ch, const QChar &ch2,
                                       const QChar &ch3, unsigned *kind,
-                                      bool wantFunctionCall);
+                                      bool wantFunctionCall, bool wantQt5SignalSlots);
 };
 
 } // namespace CppTools