Remove deprecated qMetaTypeId warning.

Remove the dummy parameter that was used for MSVC6 compatibility, and just use
it as a template function instead.

Change-Id: Id4a7e66255276dc3f2b273657b74044fcb94340e
Reviewed-by: John Brooks <john.brooks@dereferenced.net>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>