argument from addBeforeCommitHook().

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

Alas, zpkg changed since the branch was made, and it
wasn't (obviously) possible to build the branch anymore,
so much of this code didn't actually appear on the
branch.  The C code was changed to simplify and purge
non-ANSI gcc extensions, and the new test cases beefed
up a little.

in 3.8 (it didn't get released in ZODB 3.5; will be
released in ZODB 3.6).

happened in 3.6a1 (3.5a7 become 3.5 final, because 3.5a7 had
been released with Zope 3.2c1).

    
  http://permalink.gmane.org/gmane.comp.web.zope.zope3/13884

ZConfig-using zpkg; this will help keep the build-support stuff out of the
top-level directory of the checkout (such is the plan, at least)

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.