Start using ZODB 3.4, merged from Zope/branches/tim-merge-zodb34.

Looks like this may need to be a two-step checkin process.

Purged all uses of get_transaction().

lib/python/zope is now taken from tag Zope3/tags/ZopeX3-3.0.0-Zope-2.8-a2.

The 9 ZODB directories are now taken from current ZODB trunk.  A release
tag for that will be made, and Zope trunk switched to use it, later.

Unfortunately, svn refuses to update my local box to the new setup in
one step, presumably because part of this consists of deleting Zope
trunks copies of ZODB code (in favor of svn:externals).

On Windows, all tests passed on tim-merge-zodb34 branch except for the
two that have been failing for months, and without any transaction-
related deprecation warnings.

doc/ZODB.txt

@@ -58,7 +58,8 @@ The Zope Object Database, ZODB, version 3.0
 
     Don't forget to::
 
-      get_transaction().commit()
+      import transaction
+      transaction.commit()
 
     If you want any changes to made to be saved.
 

lib/python/BTrees/DEPENDENCIES.cfg

-persistent
-transaction