Normalize signal & slot signatures in connection

Profiling shows Qt Creator spends 2% of its load time normalizing

Change-Id: I7c38825875c8db58813792dcb86b3a88945466f7
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>