Include qobject_p.h from qmetaobject_p.h

Needed for QObjectPrivate::Connection. Since it's a nested class,
it's not possible to merely forward declare it.

Change-Id: Ie2ad1b3972df5433cdb49ee443f053ba2d613779
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qmetaobject_p.h

@@ -55,6 +55,9 @@
 
 #include <QtCore/qglobal.h>
 #include <QtCore/qobjectdefs.h>
+#ifndef QT_NO_QOBJECT
+#include <private/qobject_p.h> // For QObjectPrivate::Connection
+#endif
 
 QT_BEGIN_NAMESPACE