Fix QMF with Qt 5.1+

Q_GLOBAL_STATIC changed implementation. To make life easy, just make the
constructor public, and stop trying to use Q_GLOBAL_STATIC in a rather
unsupported way.

Change-Id: I7c6b13534c1a32db643574a9814b73ce0e0b22cf
Reviewed-by: Valerio Valerio <valerio.valerio@jollamobile.com>
Reviewed-by: John Brooks <john.brooks@dereferenced.net>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>