Prevent 'render' function in Expressions.py for being called for basic types (minor speed improvement).  See  http://www.zope.org/Collectors/Zope/1890. 

      - Collector #1879: applied patch by Dieter Maurer to fix a bug in 
        ac_aquire() ignoring the default argument

Collector #1864, #1906: fixed header normalization in appendHeader()

      - Collector #1899: fixed migration issue when using export/import for
        ZCatalog instances

packages than single pieces

  with Python
- remove use of the long-deprecated xmllib module, again using the Expat
  that comes with Python as a replacement

use it

In the interest of keeping myself sane, I've left the "Trunk only
(unreleased)" section alone

and not just when the file is missing. This is a forward port from Zope-2_7-branch.

        ZTUtils.make_query()

      - ZCatalog: refreshCatalog() could not be called safely from a ZEO
        client script

        problems for some .zexp files e.g. Squishdot instances)

use the pushStream/popStream model from the Zope 3 codebase instead of the
interpretWithStream model.  The two are entirely equivalent in context,
but I think the push/pop model offers more flexibility in the long run

rather then runzope to avoid all the hassle with
not detaching and thus mysteriously stopping zopes.

implementations of the TAL interpreter

Collector 1860:  use an optimistic savepoint in CopySupport._getCopy
(there's no possiblity of rollback here, so no need to insist that the
data manager support rollbacks).

The other part of this change is in ZODB 3.4.1b4, also stitched in
by this checkin.