to squash delicate code duplication and for speed.

+ This is optimized in several subtle ways over the current method.  This
  is documented in Maintainer.txt, along with a correctness proof.

+ I'll replace all the BTree searches with this soon.  For now I just
  changed _BTree_get().  I *suspect* this also fixes a subtle bug
  introduced by the recent "don't ignore comparison error" patch:  if a
  comparison did trigger an exception, the function just returned without
  doing the PER_ALLOW_DEACTIVATION + PER_ACCESSED dance.  _BTree_get()
  does that dance again now.

follows from that.

"value" to "child".  All the rest is mechanical name-changing.  Next
step is to change the decl of child from PyObject* to Sized*.

long overdue merge of toby-cmp-error-branch. btrees no longer ignore exceptions raised by the key comparison function

dumps. Copied source from 1.26.

keys at the beginning of the BTree were deleted.

Fix SF bug #516768 reported by Dave Wallace.

Replace use of PyMem_DEL() with PyObject_Del() on object dealloc
functions.  The use of PyMem_DEL() is incorrect for object
deallocation, because it only ever calls the low-level free().  If a
custom allocator like pymalloc is used, it needs to be called to free
the memory.

Also replace bare malloc() and realloc() with PyMem_Malloc() and
PyMem_Realloc().  I think this isn't a strict bug fix, but a would be
nice.  It guarantees that BTrees objects get their memory from the
same allocator as the Python core.

The code was intended to be added to the Zope3 branch, not modified on
the trunk.

bucket when doing a "low" search.

_p_resolveConflict could not handle tuples from getstate()
properly

instead of any other error that may be raised.

compilers.

they are used. This is important to keep used data structures in
memory when the ZODB garbage collector is busy.

Added Id strings.

nodes.

Optimized pickle formats (using tuple rather than tuple of tuples).

Updates Interfaces file with set operations and byValue method.

(re)Implemented new set operations and added byValue method.

Fixed bug in handling of empty BTreeItems.

Added flags to prevent subclasses from having instance dictionaries.
It's not clear that people will actually subclass these things and
supporting instance dictionaries adds extra effort at this time, which
we can't afford.

Added Sets as distinct types within template. This will make
merging sets and mapping objects (e.g. integer sets and
integer to integer mappings) easier later.

Split template into multiple files.

Change buckets to use separate key and value arrays.
This makes set handling (null value arrays) a little simpler
and will allow us to save memory if we implement types with
small keys or values (e.g. short keys).

getting key max and min values.

Added (back) PER_USE macro to make persistence handling sane.

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

Fixed numerous errors with handling bucket list pointers, deletions of
subtrees, etc.

Fixed bugs in items indexing.

Moved macros for handling specific key or value types to separate
include files. This cleaned up the code quite a bit and should make it
pretty easy to add additional types in the future.

Changed BTreeItems_length so it lies. Waaa. See comment in method.