Convert to use PyModule_*() instead of manipulating the module dict directly.

This displays stats about the # of arenas, pools, blocks and bytes, to
stderr, both used and reserved but unused.

CAUTION:  Because PYMALLOC_DEBUG is on, the debug malloc routine adds
16 bytes to each request.  This makes each block appear two size classes
higher than it would be if PYMALLOC_DEBUG weren't on.

So far, playing with this confirms the obvious:  there's a lot of activity
in the "small dict" size class, but nothing in the core makes any use of
the 8-byte or 16-byte classes.

directly.

Fix floating point exception if mpz.powm(10, 1, 0) (modulus == 0).
Add a test.

I left the email pkg alone; I'm not sure how Barry would like to handle
that.

Add test for file.readinto().

I really can't test this, but from reading the discussion in that bug
report, it's likely that this works.  It may also close a whole bunch
of other bug reports related to urllib and proxies on Windows, but who
knows.

in OSX MacPython (untested), and should be disabled/removed in OS9 (but
that doesn't happen yet).

Use METH_OLDARGS explicitly rather than implicitly.

Please review for correctness.

  Convert METH_OLDARGS -> METH_VARARGS: also PyArg_Parse -> PyArg_ParseTuple
  Convert METH_OLDARGS -> METH_NOARGS: remove args parameter
Please review.  All tests pass, but some modules don't have tests.
I spot checked various functions to try to make sure nothing broke.

These should be safe.

with each other.

the code so that the most frequent cases come first.  Added comments.
Found a hidden assumption that a pool contains room for at least two
blocks, and added an assert to catch a violation if it ever happens in
a place where that matters.  Gave the normal "I allocated this block"
case a longer basic block to work with before it has to do its first
branch (via breaking apart an embedded assignment in an "if", and
hoisting common code out of both branches).

and terminology, plus explanation of some extreme obscurities.

needs a decent commandline interface, though.

address obtained from system malloc/realloc without holding the GIL.

When the vector of arena base addresses has to grow, the old vector is
deliberately leaked.  This makes "stale" x-thread references safe.
arenas and narenas are also declared volatile, and changed in an order
that prevents a thread from picking up a value of narenas too large
for the value of arenas it sees.

Added more asserts.

Fixed an old inaccurate comment.

Added a comment explaining why it's safe to call pymalloc free/realloc
with an address obtained from system malloc/realloc even when arenas is
still NULL (this is obscure, since the ADDRESS_IN_RANGE macro
appears <wink> to index into arenas).

Else the pymalloc malloc will go insane the next time it's called.

this.  But added an overflow check just in case there is.

Got rid of the ushort macro.  It wasn't used anymore (it was only used
in the no-longer-exists off_t macro), and there's no plausible use for it.