qtwaylandscanner: fix binding delegate to track resources

Global extension objects created with qtwaylandscanner may need to track
their child resource list. This ensures bound objects are added to that
list.

Change-Id: I2875d84d2108ddad664c52ed1a11173312ff1b04
Reviewed-by: Jan Arne Petersen <jan.petersen@kdab.com>
Reviewed-by: Andy Nichols <andy.nichols@digia.com>