hotshot.stats.load.

* Use set_next() for looping in issubset() and frozenset_hash().
* Re-order the presentation of cmp and hash functions.

was never called during interpreter shutdown GC, so the f_back!=NULL
assertion was correct.  Now that generators get close()d during GC,
the assertion was being triggered because the generator close() was being
called as the top-level frame.  However, nothing actually is broken by
this; it's just that the condition was unexpected in previous Python
versions.

  a frozenset conversion when the initial search attempt fails with a
  TypeError and the key is some type of set.  Add a testcase.

* Eliminate a duplicate if-stmt.

  a frozenset conversion when the initial search attempt fails with a
  TypeError and the key is some type of set.  Add a testcase.

* Eliminate a duplicate if-stmt.

unicode instance if the argument is not an instance of basestring and
calling __str__ on the argument returns a unicode instance.

  s|=s, s&=s, s-=s, or s^=s).  Add related tests.

* Improve names for several variables and functions.

* Provide alternate table access functions (next, contains, add, and discard)
  that work with an entry argument instead of just a key.  This improves
  set-vs-set operations because we already have a hash value for each key
  and can avoid unnecessary calls to PyObject_Hash().  Provides a 5% to 20%
  speed-up for quick hashing elements like strings and integers.  Provides
  much more substantial improvements for slow hashing elements like tuples
  or objects defining a custom __hash__() function.

* Have difference operations resize() when 1/5 of the elements are dummies.
  Formerly, it was 1/6.  The new ratio triggers less frequently and only
  in cases that it can resize quicker and with greater benefit.  The right
  answer is probably either 1/4, 1/5, or 1/6.  Picked the middle value for
  an even trade-off between resize time and the space/time costs of dummy
  entries.

add st_gen, st_birthtime.

Backported to 2.4.

Backported to 2.4.

* Bring in free list from dictionary code.
* Improve several comments.
* Differencing can leave many dummy entries.  If more than
  1/6 are dummies, then resize them away.
* Factor-out common code with new macro, PyAnySet_CheckExact.

* Have issubset() control its own loop instead of using set_next_internal().

  has already done the job.
* Use a macro form of PyErr_Occurred() inside the set_lookkey() function.

* Give set_lookkey_string() a fast alternate path when no dummy entries
  are present.
* Have set_swap_bodies() reset the hash field to -1 whenever either of
  bodies is not a frozenset.  Maintains the invariant of regular sets
  always having -1 in the hash field; otherwise, any mutation would make
  the hash value invalid.
* Use an entry pointer to simplify the code in frozenset_hash().

  dictobject.c.
* Have frozenset_hash() use entry->hash instead of re-computing each
  individual hash with PyObject_Hash(o);
* Finalize the dummy entry before a system exit.

Unicode support.

'quotation mark', so I decided to use it instead of 'double-quote'.

manual.  Closes #1243553.

method still needs to support string exceptions, and allow None for the
third argument.  Documentation updates are needed, too.

  - Handle both frozenset() and frozenset([]).
  - Do not use singleton for frozenset subclasses.
  - Finalize the singleton.
  - Add test cases.
* Factor-out set_update_internal() from set_update().  Simplifies the
  code for several internal callers.
* Factor constant expressions out of loop in set_merge_internal().
* Minor comment touch-ups.