Instead, either destroy the child instead of removing it, or remove
*and* destroy it in cases where the remove() api on the "parent"
doesn't match GTK+'s parent/child relation (like with all our dock
widgets). We can't rely on remove() to implicitly detstroy, because
there might be arbitrary other code holding references, such as
accessibility modules and whatnot. Most likely fixes unclear crashes
in accessibility code and other crashes we blamed GTK+ for.