+ Added interface docs.
+ Gave it a new "newsize" argument, for when the caller can gain speed
  by knowing in advance how many additional elements are needed.  This
  isn't used yet, but will be by multiunion and planned "lopsided merge"
  optimizations (the intent is to grow the bucket big enough in one
  shot, then memcpy a large slice into the bucket).
+ When doubling the size, now sets a MemoryError exception on int
  overflow.

vanished).

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

new MULTI_INT_UNION.

dumps. Copied source from 1.26.

initial fix causes core dumps. We'll reenable this test when the bug
gets fixed (again).

Also:
    - call shuffle correctly.
    - simplify test_suite()

input sets quickly, and will become much faster again soon (see TODO
in C function multiunion_m).

keys at the beginning of the BTree were deleted.

packtime > revid1's timestamp, in a way that's immune to differences
in platform clock resolution.  Solution given by Tim Peters.

the Standby storage version of the test has a hope of succeeding.
That storage ignores non-sensically out-of-sequence tids so as written
this test wouldn't have passed until after 3220-07-29 10:18:09.882353
<methuselah wink>.

We'll use a tid that we know is earlier than now.

storage needs to be more configurable).

blather log, and optionally replays the transactions into another
storage, timing the differences between the original and the new
storage spead.

objects), read_index would fail when trying to get the max of the
nonexistent oids in the transaction.

option.

    No need to generate code that is not needed!

the cache, their changes are flushed but they're not ghostified, so
their _p_changed == 0.  For objects not in the cache, they are
ghostified and so their _p_changed == None.  The tests had the check
values reversed.

the file limit is exceeded.

Add test case for long metadata.

The simplifications focus on avoiding tests that can be done
elsewhere and on avoiding excessive use of local variable aliases for
attributes.

Move tests for too-long transaction metadata to _begin(), where the
variables are set instead of here where they are read.

fixed ZClass-related type-checking breakage introduced in reformatting in rev 1.45. I guess there are no unit tests for ZClasses?

I think it's safe to run this code without extra checking.