...in SfxPoolItem-derived classes that have a user-provided copy assignment op
(to override the explicitly deleted one of SfxPoolItem, cf.
727878a7 "Remove unused copy assignment ops of
SfxPoolItem-derived classes"), so GCC 9 would warn about the implicitly-defined
copy ctor.  Mark all those with "SfxPoolItem copy function dichotomy" comments
so they can be found again should the odd design of SfxPoolItem ever be changed.

Change-Id: If206716747c42205ae4822a3f54c9de037c75286
Reviewed-on: https://gerrit.libreoffice.org/58172
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>