Summary of changes:

- Add function gc_all_items() to call gc_item() on everything in
  dict.  This factors out common code in all the gc methods.

- Add check_size() function that factors out code to check cache size
  before starting a gc.

- Simplify argument processing in cc_invalidate(), avoiding a second
  call to PyArg_ParseTuple() when argument is a sequence instead of a
  dictionary.

- Chance code to reflect belief that NULL return from PyDict_GetItem()
  does not set exception, except in cases that don't apply for the
  pickle cache like comparing a string with high-order bit set to a
  Unicode object.

- Use if (!expr) instead of UNLESS().

- Remove all statements from conditionals.

- Reformat to 4 spaces and Python-style brace placement.

- Put whitespace around operators and after commas.

Refactor main() to report all errors and exit with non-zero status.

Remove useless -d option.

the trunk.  Sigh, if I'd known about that, I wouldn't have written
another test suite for TimeStamp. :-(

aborted.

integers, due to MS's slothful 18.2Hz updating of time.time().  The test
implicitly assumed in one spot that "the midpoint" between two revids was
strictly larger than the smaller one, but that wasn't true on Windows.
Adjusted the computation (as suggested by Guido) so that "strictly larger"
holds in the end even when the inputs are adjacent integers.

the code

    try:
        root = self._getRoot()
        ...
    except:
        self._closeDB(root)
	self._delDB()
	raise

which fails with an UnboundLocalError if the first line in the try
clause fails.  Fixed this by setting 'root = None' before each such
try clause, and adding a None check to _closeDB().  Also removed a
useless 'root = None' from the body of _closeDB().

Barry: I saw this in the saz 1.0c1 release.  Is it worth backporting?
Probably not given that we're not going to do a merge pre-1.0.

Put the tpc_begin() -> tpc_finish() in a try/except.  If an error
occurs, abort the current transaction and re-raise the error.

It appears that some storages (well, only Standby Storage) has trouble
shutting down if a transaction is in progress.

Replace three small integers with symbolic constants.
    TRANS_HDR_LEN = 23
    DATA_HDR_LEN = 42
    DATA_VERSION_HDR_LEN = 58
The constants make it easier to remember what kind of header is being
read and/or what kind of offset is being computed.

Refactor commitVersion():
    - Keep locking & arg checking in commitVersion(), but move actual
      commit logic to _commitVersion().  This removes a level of
      indentation.

    - Remove local vars that alias attributes of other vars

Add a few more POSKeyError exceptions.

Highlights:

BaseStorage.py:

Fix copyTransactionsFrom() when commitVersion(), abortVersion() or
transactionalUndo() is used.

FileStorage.py:

Add restore() method, which can store data records corresponding to
undo or version manipulations; add close() method to FileIterator
class; raise POSKeyError instead of KeyError for bad keys, to ensure
safe formatting of transaction ids (binary strings) in tracebacks.

POSException.py:

Add POSKeyError.

fsdump.py:

Deal with records indicating the undo or abort of a version doing
object creation.

tests/IteratorStorage.py:

New unittests for the iterator() method and interface of the
storage API; new unit tests for extended file iterators; new class,
IteratorDeepCompare; test of the iterator .close() method.

tests/testFileStorage.py:

Add class FileStorageRecoveryTest, which adds two simple tests for
copyTransactionsFrom().  This indirectly tests the new restore()
method.

1. The exception is in serial, not arg.
2. Must call handle_serials() before tpc_finish(), because
   handle_serials() may raise an exception that causes the transaction
   to abort.

The main test suite handles ZEO now.

Laredo.  [merging from Recovery branch into trunk]

Py_None.

Make sure that the test undoes an object creation and make sure that
the iterator for that transaction return None for the data attribute.

This will allow an iterator to handle aborted versions and undone
object creations.  XXX Still need a test for the latter.

XXX checkTransactionalUndoIterator() should too, but doesn't.