Try to make more sense of the ZODB pickle format "docs".

Document _p_invalidate().

Now use ZODB.utils.z64 instead of '\0\0\0\0\0\0\0\0' where appropriate.

Connection.root():  Repair error in docstring.

Remove duplicate declaration and definition of py___getstate__.

Duplicate import removed.

See Collector #1350.

ghostify() and unghostify() detect one form of thread insanity
now.  In a debug build, they abort the process if it happens.
In a release build, unghostify() raises SystemError, and
ghostify() ignores it (ghostify() can't raise an exception).

before I went on vacation a couple weeks ago.

This rehabilitates the good part of Andreas's change; adds
news; adds comments; and adds more comments about the
sequence of undocumented cPickle gimmicks this relies on.

Collector #1517: History tab for ZPT does not work

FileStorage.history() was reading the user, description,
and extension fields out of the object pickle, due to
starting the read at a wrong location.

Restore the Connection._opened attribute, actually used by
DB.connectionDebugInfo().

Typo repair.

os.listdir() now prints errors on stdout

When raising DeprecationWarning, point the warning machinery at
the caller, not at Transaction.begin() itself.  As is (voice
of experience <wink>), these warnings are darned near useless to
track down code that needs to be changed on Zope trunk.  With the
change, the warnings point directly at the deprecated uses.

Rev 26842 changed cache-size parameters to type byte-size.
That's a good change, but it was checked in from a wrong place
(from the Zope trunk's copy of ZODB).  Since we want Zope 2.8 to
be usable with ZODB 3.3 too, I need to slam this change into
3.3 now.

Alas, I don't understand how ZODB+ZEO got stitched into the
Zope trunk (I do understand how it got stitched into the
Zope3 trunk, and into the X3 branch), and it looks like that
was left in a poor state.

So that if Zope X3-3.0 final is released while I'm on vacation,
it will have the right ZODB stuff in it (although I still need
to stitch this in to the Zope 3 and X3 trees).

This confirms that 3.3 didn't have the 3.2.4c1 bug wherein
an explict transaction abort() failed to clear Connections'
memory of ReadConflictErrors.

be.  Besides "the usual" release fiddling, repaired many
out-of-date pieces of the ZODB programming guide; I'm sure
many remain, though.

transaction when a commit() fails.  One test here provoked a
failing commit(), which caused a later test to fail.  Repaired
by simply abort()'ing the failed transaction.

After a commit fails (raises an exception), all subsequent attempts
to commit, join, or register with the transaction now raise the new
TransactionFailedError.  The failed transaction must be explicitly
discarded now, via abort() on the transaction or begin() on its
transaction manager.

more was incomprehensible.  Tried to repair that.  Plus
random improvements to ReST markup.

The ConflictError.get_{old,new}_serial() methods each did what the other
was supposed to do.

Collector #1488 (TemporaryStorage -- going backward in time).

This confusion was really due to that the detail on a ConflictError
exception didn't make sense.

Forward port from Zope 2.7 branch.

_handle_independent():  Failed to record that a ReadConflictError
was raised for an object with a _p_independent() method that
returned false.

is made while the connection has a pending subtransaction.

begin() is supposed to abort the current transaction, but
Transaction.begin() did not.  Calling begin() on a transaction
*manager* worked fine, and is the intended way to do a begin()
in 3.3.  But calling begin() on a Transaction object is still
very easy to do (e.g., the older get_transaction().begin()
spelling still works), and shouldn't be a subtle disaster.

creating problems.

started with a pickle GLOBAL opcode.  Curiously, it handled the
case of starting with a MARK GLOBAL opcode *sequence* fine.

FileIterator.next():  the code for reading the user, description,
and extension fields from a transaction was fatally confused,
usually reading them out of the object pickle by mistake.  This
caused several tools to display binary gibberish.

analyze_rec():  This produced spurious "len of unsized object" messages
when a data record had a backpointer instead of a pickle.  Repaired.

analyze(), analyze_trans():  Simplified overly elaborate iteration code.

Many changes to fsrefs.py, based on problems I hit using it in real life.