weld::TreeView and weld::IconView implement the same
logic for signalling about selection changes.
Deduplicate that by moving it to the weld::ItemView
base class.
Change-Id: Ie749ca45cf7da76faf38e8e42eb9a41346f00856
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/203368
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Tested-by: Jenkins
Michael Weghorn
de2a389734