use qt_qmlIdForObject to set the name of a qml obj

this needs a special patch in Qt, make sure it's there before you enable
it, with 'CONFIG+=qml_id'!

see:
http://gitweb.merproject.org/gitweb?p=mer-core/qt.git;a=blob;f=0029-Add-internal-qt_qmlIdForObject-to-retrieve-the-id-fo.patch;h=2571c2f21ceef29c7064de1daa1a150636bb21e1;hb=HEAD