Fix IdTemplate.
Fix IdTemplate.

The current implementation makes *all* instantiations of our qHash()
template a friend of IdTemplate, whereas the new one limits it to the
one instantiation matching the class.

Change-Id: I816b595bc10d593bb90b9b12f4525ff792ac447e
Reviewed-by: Joerg Bornemann <47777b9406dbddd02a3fdca8341789a013805a11@digia.com>

villytiger/qbs,gatzka/qt-labs-qbs,qtproject/qt-labs-qbs,villytiger/qbs,villytiger/qbs,Distrotech/qbs,villytiger/qbs,Distrotech/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,gatzka/qt-labs-qbs,Distrotech/qbs,villytiger/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,villytiger/qbs,qt-labs/qbs,Distrotech/qbs,gatzka/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,gatzka/qt-labs-qbs,gatzka/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,Distrotech/qbs,gatzka/qt-labs-qbs,qt-labs/qbs,Distrotech/qbs,Distrotech/qbs,qt-labs/qbs,gatzka/qt-labs-qbs