...offload to init() instead and wrap ctor in create().  That removes the need
for refcount fiddling and additional OContainerListener class.  Which in turn
removes code using dynamic_cast on UNO interface classes, which my claim at
<http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20130812/
086127.html> "ubsan: check type_info equality via strcmp" that "there should not
be uses of dynamic_cast involving [UNO] classes in the LibreOffice code base"
made me wonder about...

Change-Id: I5d72650f6bf081f971f7bd6bb65f4e58a342f791