- In ``skel/etc/zope.conf.ing``, replaced commented-out
  ``read-only-database`` option, which is deprecated, with pointers to the
   appropos sections of ZODB's ``component.xml``.

- Updated the description of the ``zserver-read-only-mode`` directive to
  indicate its correct semantics (suppressing log / pid / lock files).
  
- Added deprecation to the ``read-only-database`` option, which has had no
  effect since Zope 2.6.