causing extra pain on windows.

accross revs.

after conflict errors on blobs. :(

servers much easier. This was easier than I expected. I should have
done this a long time ago. :)

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- The helper function ZODB.blob.is_blob_record didn't handle having
  None passed to it, but database "delete" records have None for their
  data.

- CVE-2009-2701: Fixed a vulnerability in ZEO storage servers when
  blobs are available. Someone with write access to a ZEO server
  configured to support blobs could read any file on the system
  readable by the server process and remove any file removable by the
  server process.

Fixed to use a separate Random instance.

----------

- BTrees (and TreeSets) kept references to internal keys.
  https://bugs.launchpad.net/zope3/+bug/294788

- BTree Sets and TreeSets don't support the standard set add method.
  (Now either add or the original insert method can be used to add an
  object to a BTree-based set.)

setuptools installed.

https://bugs.launchpad.net/zodb/+bug/185066

The fix didn't go far enough and a fix that would go far enough would
be too risky this late in the 3.9 beta cycle.  This will probably need
to wait till 3.10.

  Certain ZEO server errors could cause a client to get into a state
  where it couldn't commit transactions.
  https://bugs.launchpad.net/zodb/+bug/374737

  Savepoint blob data wasn't cleaned up after a transaction abort.
  https://bugs.launchpad.net/zodb/+bug/323067

  When committing transactions involving blobs to ClientStorages with
  non-shared blob directories, a failure could occur in tpc_finish if
  there was insufficient disk space to copy the blob file or if the
  file wasn't available.  https://bugs.launchpad.net/zodb/+bug/224169

Now link/copy file when storeBlob is called.

  Objects defining _p_deactivate methods that didn't call base methods
  weren't loaded properly. https://bugs.launchpad.net/zodb/+bug/185066

for objects that don't use slots, which are the vast majority of
persistent objects.

while cleaning up removed blob files.

Also refactored the code slightly for clarity.