QObject: add a macro for conveniently setting the object name

QObject: add a macro for conveniently setting the object name

This is a simplified port of KDTools' KDAB_SET_OBJECT_NAME.
It simply assigns the variable name as the objectName of
a QObject, uic-style. It uses a small helper function so
that it works on references as well as pointer variables.

  QLabel label;
  QLabel *pLabel = new QLabel();
  Q_SET_OBJECT_NAME(label);
  Q_SET_OBJECT_NAME(pLabel);

Change-Id: I25fec0c90f33249a3ea5d2dd622ab708019fd101
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
Reviewed-by: David Faure <faure@kde.org>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>