Fix test_sys.test_getallocatedblocks() when tracemalloc is enabled.
If the name of Python memory allocators cannot get read, consider
that pymalloc is disabled.

Fix the following error:

./python -X tracemalloc -m test test_sys -v -m test_getallocatedblocks

ERROR: test_getallocatedblocks (test.test_sys.SysModuleTest)
------------------------------------------------------------
Traceback (most recent call last):
  File "Lib/test/test_sys.py", line 770, in test_getallocatedblocks
    alloc_name = _testcapi.pymem_getallocatorsname()
RuntimeError: cannot get allocators name

"make tags" and "make TAGS" now also parse Modules/_io/*.c
and Modules/_io/*.h.

Modify CLEANBYTE, DEADDYTE and FORBIDDENBYTE constants: use 0xCD,
0xDD and 0xFD, rather than 0xCB, 0xBB and 0xFB, to use the same byte
patterns than Windows CRT debug malloc() and free().

Commit 57b1a286 fixed doctest, but example code is not
match with document.
Just skip doctest for the block.

Replace _PyMem_IsFreed() function with _PyMem_IsPtrFreed() inline
function. The function is now way more efficient, it became a simple
comparison on integers, rather than a short loop. It detects also
uninitialized bytes and "forbidden bytes" filled by debug hooks
on memory allocators.

Add unit tests on _PyObject_IsFreed().

Disable the job to unblock the CI until the issue is properly
understood.

* better __init__.py explanation in tutorial

* Update Doc/tutorial/modules.rst
Co-Authored-By: methane <songofacandy@gmail.com>

Set CUSTOMIZED_OSX_COMPILER to True to disable
_osx_support.customize_compiler().

The random module now prefers the lean internal _sha512 module over hashlib
for seed(version=2) to optimize import time.
Signed-off-by: Christian Heimes <christian@python.org>

The script needs to be updated to support win 10/ 1803 chcp.com command (output has trailing dot)





https://bugs.python.org/issue34144

Fixes some mistakes and misleadings in the quote function docstring:
- reserved chars are never actually used by quote code, unreserved chars are
- reserved chars were wrong and incomplete
- mentioned that use-case is not minimal quoting wrt. RFC, but cautious quoting

Fix time.mktime() error handling on AIX for year before 1970.

Other changes:

* mktime(): rename variable 'buf' to 'tm'.
* _PyTime_localtime():

  * Use "localtime" rather than "ctime" in the error message
    (specific to AIX).
  * Always initialize errno to 0 just in case if localtime_r()
    doesn't set errno on error.
  * On AIX, avoid abs() which is limited to int type.
  * EINVAL constant is now always available.

[bpo-36146](https://bugs.python.org/issue36146) introduced another regression. In case of missing OpenSSL
libraries or headers, setup.py no longer reported _hashlib and _ssl to
be missing.
Signed-off-by: Christian Heimes <christian@python.org>



https://bugs.python.org/issue36577

dash_R() function of libregrtest doesn't call support.gc_collect()
directly anymore: it's already called by dash_R_cleanup().

Call dash_R_cleanup() before starting the loop.

python-config --ldflags no longer includes flags of the LINKFORSHARED
variable. The LINKFORSHARED variable must only be used to build
executables.

https://bugs.python.org/issue36544

https://bugs.python.org/issue34139

Fix reference leak hunting in regrtest: compute also deltas (of
reference count, allocated memory blocks, file descriptor count)
during warmup, to ensure that everything is initialized before
starting to hunt reference leaks.

Other changes:

* Replace gc.collect() with support.gc_collect()
* Move calls to read memory statistics from dash_R_cleanup() to
  dash_R()
* Pass regrtest 'ns' to dash_R()
* dash_R() is now more quiet with --quiet option (don't display
  progress).
* Precompute the full range for "for it in range(repcount):" to
  ensure that the iteration doesn't allocate anything new.
* dash_R() now is responsible to call warm_caches().

While Windows exposes the system processor queue length, the raw value
used for load calculations on Unix systems, it does not provide an API
to access the averaged value. Hence to calculate the load we must track
and average it ourselves. We can't use multiprocessing or a thread to
read it in the background while the tests run since using those would
conflict with test_multiprocessing and test_xxsubprocess.

Thus, we use Window's asynchronous IO API to run the tracker in the
background with it sampling at the correct rate. When we wish to access
the load we check to see if there's new data on the stream, if there is,
we update our load values.

Move all documentation regarding the readinto method into either io.RawIOBase or io.BufferedIOBase.

Corresponding changes to documentation in the _pyio.py module.

It turns out doing socket.listen(0) does not equal to "choose a
reasonable default". It actually means "set backlog to 0".
As such set backlog=None as the default for socket.create_server.
Fixes the following BB failures:
https://github.com/python/cpython/pull/11784#issuecomment-481036369
Ref. BPO-1756, GH-11784.

Fix reference hunting (``python3 -m test -R 3:3``) when Python has no
built-in abc module: fix _get_dump() reimplementation of libregrtest.