This enables a QtVersionFactory to be able to create more than one
QtVersion, which can make sense e.g. if there are several closely
related ones.

Change-Id: I597f524abfc27c483c71bb6567ce7b77bc3d3041
Reviewed-on: http://codereview.qt.nokia.com/835


Reviewed-by: Daniel Teske <daniel.teske@nokia.com>