Fix bug reported by John D. Heintz.

"supportsTransactionalUndo()" method.

XXX untested

XXX This mechanism for feature evolutional doesn't seem right, because
it because a morass of backwards compatibility issues.  I'd rather see
the test by one of presence/absence of an attribute or a base class.

storage in all their many flavors.

This fixes a conflict resolution bug with subtransactions.
XXX Commit same change of zope-2_3-branch.

A related change in store() is to call _handle_serial() *after*
putting new objects in the cache.  This simplifies the logic of
_handle_serial() a bit, because every object should be in the cache.

sub-transactions

XXX Need to apply effbot's lambda-refactoring pattern

Use types module rather than type().
Fix indentation nit.

misnamed, because it's also the min_connect_poll and it makes the
tests run much faster by waiting for a shorter period of time between
connect attempts.)

Add makeTestSuite() helper that replaces clunky unittest mechanisms.

any recent updates are written to the file.

Remove seek() and tell() at the beginning of read_index() because
their results are not used.

Add main() that prints the contents a cache file when executed as a
script.

Add a log call when the cache is being read.

Add optional cache_size argument.

Also print # conflicts for each test (appears to be zero).

different depending on whether the version is different.

The invalidated oids (and versions) get written to the tempfile, and
are invalidated during the tpc_finish().

separate class

Support for using basic multi framework with other run() functions.

XXX The two cache invalidation tests fails currently.

storage id

The cdata and cver had been swapped, causing all undos to fail,
because the version was compared to a pickle.

checkBuggyResolve2() -- _p_resolveConflict takes too few args
checkUndoConflictResolution() -- make sure conflict resolution is
     invoked properly during transactional undo
checkUndoUnresolvable() -- make sure transactional undo can cope with
     failed conflict resolution

Add new tests for conflict resolution.

The old blanket try-except for conflict resolution was hiding some
bugs caused by the pickles used in the test suite.  The conflict
resolution code imposes some restrictions on the format of pickles.
Basically, the conflict resolution requires that the storage API only
accept a pickles that constructed according to the ZODB rules.

XXX This new restriction sounds unfortunate, but it would require a
substantial change to conflict resolution to remove it.

The key changes to the test suite are to store only persistent objects
and to format the pickles using the standard ZODB format.  All tests
now use ZODB.tests.MinPO.MinPO instances for data.  The pickling is
down with zodb_pickle() and zodb_unpickle() defined in
StorageTestBase.

Add conflict resolution tests to testFileStorage.  (They pass.)

The value of _loadBack() -- a pickle and a serialno -- was being
passed to tryToResolveConflict() where only a pickle was expected.

XXX _loadBack() can raise KeyError, but this wasn't handled by the
code.  Turn into UndoError() for now.

exactly one exception, ConflictError

Remove klass._p_resolveConflict line, because it's only apparent
purpose was to raise an AttributeError that was caught by the blanket
try-except.  Instead, let the later code, which actually uses
_p_resolveConflict() catch the AttributeError and return 0.

Add -t n flag to specify number of concurrent threads
Add -U flag to specify a Unix domain socket