check the length after convering to a list, because btree items
have to lie about their length.

include files. This cleaned up the code quite a bit and should make it
pretty easy to add additional types in the future.

the subtransactions.

in cases where a transaction is aborted due to a storage error
(e.g. ConflictError) during two-phase commit and new objects
have been stored. The new objects were left in a state where they
incorrectly appeared to have been saved and be up to date.

Also removed unnecessary invalidation of objects in other connections
when commiting sub-transactions.

Merged in changes from Evan's branch that allows the system to
continue commiting transactions when there is a failure of only one
data manager in the last phase of two-phase commit.

inconsistent data. Added a detailed comment with explanation.

Added explanation of the semantics for calling the function passed to
the storage tpc_finish method.

important for ZEO, which may need to get tickled to get updates in
non-aynchronous mode.

This was to get a newer asynccore (or ZServers) if possible.

to database connection leaks when the mount point object was garbage
collected.

if an attempt was made to write while disconnected from the storage
server.

defaults to the present and a 'days' keyword argument can be used to
specify a number of days pervious to the time to pack to.

A wait keyword argment can be provided for pack that causes the client
to wait for a pack response from the server. NOTE: no other requests
will be sent to the server while waiting for the pack response. This
feature should only be used from utility packing scripts.

Got rid of the no-longer-used (synchronous) store method.

Added a wait argument to pack.  If the wait argument is provided,
then the pack method doesn't return a value till packing is done.

Simplified the way errors are handled in normal calls and
packs by putting the error marshalling logic into a separate
method.

No longer log UndoError, VersionCommitError, and TransactionError
exceptions on the server, since these are user-level errors.

Do log pack errors.

defaults to the present and a 'days' keyword argument can be used to
specify a number of days pervious to the time to pack to.

Rearranged handlers to make them a little less signal dependent.

"address already in use" errors.

editorial changes.