Thanks to the new pytypedefs.h, it becomes to use type names like
PyObject rather like structure names like "struct _object".

As part of the PEP-652 implementation, I'll tighten the CI check
for functions/data defined with `Py_LIMITED_API`.

Discussion in https://discuss.python.org/t/pep-652-maintaining-the-stable-abi/6986
suggests that parsing C headers is OK (though personally I'd rather generate it...),
but writing a full C parser is a monumental task and adding an existing one as a
dependency brings too many vendoring/bootstraping issues.

So, for the check I'll use a "simple" regex on preprocessor output, and adapt
the few trivial places where the regex won't work.

- Keep declarations in the limited API to one item per line
- Make it possible to override `_Py_NO_RETURN`, so the annotation can be
  removed from preprocessor output.


https://bugs.python.org/issue43795

Add the Py_Is(x, y) function to test if the 'x' object is the 'y'
object, the same as "x is y" in Python. Add also the Py_IsNone(),
Py_IsTrue(), Py_IsFalse() functions to test if an object is,
respectively, the None singleton, the True singleton or the False
singleton.

Added Py_NewRef() and Py_XNewRef() functions to increment the reference
count of an object and return the object.

Co-Author: Neil Schemenauer <nas-github@arctrix.com>

svn+ssh://pythondev@svn.python.org/python/branches/p3yk

................
  r56477 | martin.v.loewis | 2007-07-21 09:04:38 +0200 (Sa, 21 Jul 2007) | 11 lines

  Merged revisions 56466-56476 via svnmerge from
  svn+ssh://pythondev@svn.python.org/python/trunk

  ........
    r56476 | martin.v.loewis | 2007-07-21 08:55:02 +0200 (Sa, 21 Jul 2007) | 4 lines

    PEP 3123: Provide forward compatibility with Python 3.0, while keeping
    backwards compatibility. Add Py_Refcnt, Py_Type, Py_Size, and
    PyVarObject_HEAD_INIT.
  ........
................
  r56478 | martin.v.loewis | 2007-07-21 09:47:23 +0200 (Sa, 21 Jul 2007) | 2 lines

  PEP 3123: Use proper C inheritance for PyObject.
................
  r56479 | martin.v.loewis | 2007-07-21 10:06:55 +0200 (Sa, 21 Jul 2007) | 3 lines

  Add longintrepr.h to Python.h, so that the compiler can
  see that PyFalse is really some kind of PyObject*.
................
  r56480 | martin.v.loewis | 2007-07-21 10:47:18 +0200 (Sa, 21 Jul 2007) | 2 lines

  Qualify SHIFT, MASK, BASE.
................
  r56482 | martin.v.loewis | 2007-07-21 19:10:57 +0200 (Sa, 21 Jul 2007) | 2 lines

  Correctly refer to _ob_next.
................

I banged on the code (beyond what's in that branch) to make fewer tests fail;
the only tests that fail now are:
  test_descr -- can't pickle ints?!
  test_pickletools -- ???
  test_socket -- See python.org/sf/1619659
  test_sqlite -- ???
I'll deal with those later.

Rewrote Py_RETURN_{NONE, TRUE, FALSE} to expand to comma expressions
rather than "do {} while(0)" thingies.  The OP complained because he
likes using MS /W4 sometimes, and then all his uses of these things
generate nuisance warnings about testing a constant expression (in
the "while(0)" part).  Comma expressions don't have this problem
(although it's a lucky accident that comma expressions suffice for these
macros!).

to handle situations like ``if (foo) Py_RETURN_NONE else ...``.