This adds .setdefault() methods to BTrees and Buckets.

- note the zpkg command line that should be used
- remove Persistence from the resource map
- remove SETUP.cfg now that it is not needed

update_from_seq():  If PySequence_Check(seq) returns true,
go on to check for the existence of "iteritems" when deciding
whether the input is or is not "a sequence".  Alas,
PySequence_Check() does return true for PersistentMapping and
PersistentDict instances, so that they couldn't be used as
arguments to BTree/Bucket construction or update().

This is nasty type-sniffing, but it was before too.  There's
no way to make such stuff bulletproof, so I'm settling for
incremental improvement.

``svn move`` does an add and a delete.  This is the delete part.
The add to Zope trunk happened in rev 38103.

Comment out the undocumented method definitions in the
storage interfaces.  It would be better to define &
document them, but that takes time, and until time is
available better not to pretend that they're all really
part of "the" storage API.

Gave PersistentMapping an __iter__ method.

Also gave it some tests (it was woefully untested).

  for packaging metadata; zpkg can take care of that for us
- restore the copyright year, which made sense
- restore the VERSION constant and the comment I should have read

(not strictly necessary, but keeps different projects on similar footings)

Code and new test to ensure that making a savepoint triggers cache gc.

the new addBeforeCommitHook() method of transactions.

Minor, unrelated changes in release.py.

addBeforeCommitHook() is new, a generalization of the
now-deprecated beforeCommitHook() that allows influencing
the order in which commit hooks are called.

[Martijn Pieters]
Include INSTANCE_HOME in the runzeo and zeoctl startup scripts from
the get-go; this helps poor schmucks like me who have to make
app-level conflict resolution work in Products as well. Including
INSTANCE_HOME makes sure ZEO can find the product code in the first
place.

- References to headers now involve the package names.

- The zpkg support files have been moved to the top-level directory,
  and the releases/ tree has been removed.  The resource map and
  configuration file have been combined now that zpkg allows that.

- The scripts are now all located in src/scripts/ in a checkout.

- Scripts that were imported in the tests have been split into library
  and script components; the library portions share name of the
  script (in order to reduce changes).  The library portions may not
  be used as scripts directly.

More on collector 1847 (ZEO cache tracing).

simul.py hit NameErrors when startup cache verification
found data in the cache to invalidate.

The cache's loadBefore() implementation called _trace()
incorrectly, passing the tid where the version argument
belonged.

Part of Collector 1860 (the other part is in Zope).

There's no possiblity of rollback here, so no need to insist that the
data manager support rollbacks.

Plug leaks in the ZEO client cache.

ClientCache._evicted():  When deleting the last range of
non-current tids for an oid, remove the list from the
noncurrent dict instead of leaving an empty list sitting
there forever.  This also required adjusting the side-
effect dance in ClientCache._remove_noncurrent_revisions().

FileCache._makeroom():  This was the major leak -- it
neglected to remove an evicted object's Entry from the
key2entry dict.

  move things around so that zeo scripts are installed for
  standalone zodb releases but not for zope releases

Needs to import errno now.

Worm around suspected Windows socket bug in Windows trigger code.

See the thread starting at
 http://mail.zope.org/pipermail/zope/2005-July/160433.html
for gory details.

makeroom():  Simplify retrieve+del from filemap.

Removed the `key2size` OIBTree.

Maintaining this is a significant expense; the code didn't
make real use of it; and every time I've tried to exploit it
I've ended up with grossly too-large simulated hit rates.
Would probably take another day to figure out exactly why that
is, and the simulated rates are "good enough" now without it.

More words; update examples w/ new output.

The cache simulation seems good enough to be useful now,
although the toy app I wrote to generate a 500MB trace
file doesn't use MVCC in an essential way (some of the
MVCC simulation code is nevertheless exercised, since
an invalidation of current data in the presence of MVCC
always creates a cache record for the newly non-current
revision).

Still puzzling over what to do when the trace file records
a load hit but the simulated cache gets a miss.  The
old simulation code seemed to assume that a store for the same
oid would show up in the trace file next, and it could get
the info it needed about the missing object from the store
trace.  But that isn't true:  precisely because the load was
a hit in the trace file, the object isn't going to be stored
again "soon" in the trace file.

Here are some actual-vs-simulated hit rate results, for a
20MB cache, with a trace file covering about 9 million
loads, over 3 ZEO client (re)starts:

actual   simulated
------   ---------
  93.1        92.7
  79.8        79.0
  68.0        69.1
      
  81.4        81.1  overall

Since the simulated hit rates are both higher and lower
than the actual hit rates, that argues against a gross
systematic bias in the simulation (although there may
be several systematic biases in opposite directions).

Massive rewrite to make simul.py's circular cache aware of
MVCC.  It isn't blowing up, but it thinks the hit rate is
100% -- might have missed something there <wink>.

More steps on the way toward having useful cache simulation.

I think the primary hangup now is that simul.py doesn't know
anything about MVCC.  As a result, it thinks there's significatly
more free space in the cache than there really is, and that
probably accounts for it predicting significantly higher hit
rates than I actually see.