Blender would have crashed when renaming bone in Edit Mode, Saving, and
than selecting/deselecting.

Caused by a mistake in the 0f89bcdbebf5: can not "short-circuit" the
CoW update if it was explicitly requested.

Safest for now solution seems to be to store whether the CoW component
has been explicitly tagged, so that the following configuration can be
supported:

DEG_id_tag_update(id, ID_RECALC_GEOMETRY);
DEG_id_tag_update(id, ID_RECALC_COPY_ON_WRITE);