Normalize signal & slot signatures in connection

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

Change-Id: I793aea0f46cc74f6466e52d00c0ec868c6603c77
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>