(Forward-port from 3.8 branch)

- winlock.c does not exist anymore, so do not try to compile it. This 
  only affects zpkg.

- Ignore a generated file.

(hang). This was accomonied by a critical log message along the
lines of: "RuntimeError: dictionary changed size during iteration".

preventing it.

2.4 and 2.5.

and 2.5.

document conflict resolution. bugfix the situation in which comparing persistent objects (for instance, as members in BTree set or keys of BTree) might cause data inconsistency during conflict resolution.  support multidatabase references in conflict resolution.  make it possible to examine oid and (in some situations) database name of persistent object references so that I can add some code to zope.app.keyreference to support these objects (so BTree conflict resolution can happen at all when keyreferences are used).  I will add information to CHANGES after Jim reviews (or sooner).

Added APIs for removing committed blob data that makes files writable
before removing them and updated code that removes committed blobs or
blob directories to use them.

stack traces.

spurious failures.

that it is specific to blobs. Added logging when we have to copy.

willing to copy when renaming fails.

savepoint storage.

Also added a test for the normal blob case.

if we can't link.

Added support for copying to blob cache when renaming fails.

committed file name.

Make sure that uncommitted data gets cleaned up if w blob is GCed
without committing.

 - some cleanups
 - re-introduced a way to ask for a rename() operation but fall back to copy
   if rename doesn't work
 - using the rename_or_copy for blobs where reasonable
 - fixed a test that was trying to test a failing consumeBlob but where the
   wrong exception was tested for

   new uncommitted data.
 - Made blobs use the temporaryDirectory() method of storages to store new
   uncommitted data near the committed data.

Removed the soon to be replaced readDetached,