Zope3/ZODB4.  Many test fixes from Jeremy (in particular,
most of the tests weren't getting run), and new tests from
Tim.  Note that the new testEmptyBucketConflict() actually
shows that a particular rare case of conflict resolution
doesn't work correctly now.  A fix for that comes next,
along with reversing the sense of this new test.

repitition and no magical guessing of type names in the datatypes.

language.

- minor markup changes

component provided with zLOG.

- add at least something of a test for the datatype

Handing off to Barry.

ZEO.Exceptions.ClientDisconnected will always be raised when a client
is disconnected.  There's also a subclass of this exception in
ZEO.zrpc.error so that it's possible to distinguish whether the error
occurred in the RPC layer or at the storage layer.

If the client isn't connected at all, sync() returns quickly and the
test fails because it doesn't wait long enough for the client.

- convert hostnames to lower case

XXX Don't expect port 9 to do anything on any machine.

is check.check(btree), which performs value-based sanity checks on a
BTree (or TreeSet) that the btree._check() method doesn't do.  The new
checks include that all the bucket keys are in sorted order, and that
all the keys within each bucket, and within each internal BTree node,
lie within the range necessary for that node.  That last is a subtle
invariant that can't be checked locally:  it requires propagating range
info down the tree, and modifying it for each child and each level.
This *should* catch any BTree B for which iterating over the keys yields
a key K for which B.has_key(K) returns false.

Another function check.display(btree) prints the internal structure of
a BTree (or TreeSet, Bucket, or Set) to stdout.  If check.check(B) ever
complains, a clearer picture of the damage can be gotten by staring at
check.display(B)'s output.

Also beefed up the regular BTree tests by calling check.check() in key
places.  No surprises (the tests still pass).

XXX Maybe there should be an option to allow this.

A ZEO client can run in disconnected mode, using data from
its cache, or in connected mode.  Several instance variables
are related to whether the client is connected.

_server: All method calls are invoked through the server
   stub.  When not connect, set to disconnected_stub an
   object that raises ClientDisconnected errors.

_ready: A threading Event that is set only if _server
   is set to a real stub.

_connection: The current zrpc connection or None.

_connection is set as soon as a connection is established,
but _server is set only after cache verification has finished
and clients can safely use the server.  _pending_server holds
a server stub while it is being verified.

Before this change, a client could start using a connection before
verification finished.  If verification took a long time, it could
even commit a new transaction using a mixing of old and new data.

Pending does reads and writes.  In the case of server startup, we may
need to write out zeoVerify() messages.  Always check for read status,
but don't check for write status only there is output to do.  Only
continue in this loop as long as there is data to read.

test.

with StorageTypes.

conversion.

updated, which resulted in one whole cache being kept for no reason.

2 so they aren't normally run.

(ReconnectionTests make no sense for MappingStorage).

Also add BDBTimeoutTests.

Set the level for the FileStorageConnectionTests,
FileStorageTimeoutTests, BDBConnectionTests, BDBReconnectionTests, and
BDBTimeoutTests to level 2 so they aren't normally run.

MappingStorageConnectionTests and MappingStorageTimeoutTests both get
level 1 so they are normally always run.  FileStorageReconnectionTests
also gets level 1 since there s no MappingStorageReconnectionTests.

complete.

string to socket connect(), used 'localhost' instead).

much via the xmlmarkup environment definitions.