Move them inside the vcl module. there is no need to expose their
implementation.
Make the VclEventListeners2 implementation similar to the
VclEventListeners implemenation - I can't see the benefit of this extra
complication with invalidated iterators, given the very small number
of listeners typically on such a list.

Change-Id: I040ddd24b10d2109af13ee25b5181703af17a109