GetTickCount64() is now always available.

In practice, _PyTime_t is a number of nanoseconds. Its C type is a 64-bit
signed number. It's integer value is in the range [-2^63; 2^63-1]. In seconds,
the range is around [-292 years; +292 years]. In term of Epoch timestamp
(1970-01-01), it can store a date between 1677-09-21 and 2262-04-11.

The API has a resolution of 1 nanosecond and use integer number. With a
resolution on 1 nanosecond, 64-bit IEEE 754 floating point numbers loose
precision after 194 days. It's not the case with this API. The drawback is
overflow for values outside [-2^63; 2^63-1], but these values are unlikely for
most Python modules, except of the datetime module.

New functions:

- _PyTime_GetMonotonicClock()
- _PyTime_FromObject()
- _PyTime_AsMilliseconds()
- _PyTime_AsTimeval()

This change uses these new functions in time.sleep() to avoid rounding issues.

The new API will be extended step by step, and the old API will be removed step
by step. Currently, some code is duplicated just to be able to move
incrementally, instead of pushing a large change at once.

add a version changed note in modified functions.

in debug mode to detect bugs earlier.

_PyUnicodeWriter_Finish() doesn't check if the read only string is consistent,
whereas it does check consistency for strings built by itself.

as repr().

creation) mode.

close the binary file to fix a resource warning.

Flushing sys.stdout and sys.stderr in Py_FatalError() can call again
Py_FatalError(). Add a reentrant flag to detect this case and just abort at the
second call.

writer failed in BufferedRWPair.close().

keyword argument.  string.Formatter now allows to specify the "self" and
the "format_string" parameters as keyword arguments.

It should help to see exceptions when stderr if buffered: PyErr_Display() calls
sys.stderr.write(), it doesn't write into stderr file descriptor directly.

* Display the current Python stack if an exception was raised but the exception
  has no traceback
* Disable faulthandler if an exception was raised (before it was only disabled
  if no exception was raised)
* To display the current Python stack, call PyGILState_GetThisThreadState()
  which works even if the GIL was released

Issue #23654: Turn off ICC's tail call optimization for the stack_overflow
generator. ICC turns the recursive tail call into a loop.

Patch written by Matt Frank.

GzipFile corruption.  Original patch by Wolfgang Maier.

Issue 23729:  Document ElementTree namespace handling and fix an omission in the XPATH predicate table.

Some http servers will reject PUT, POST, and PATCH requests if they
do not have a Content-Length header.

Patch by James Rutherford, with additional cleaning up of the
'request' documentation by me.

Patch by Mike Short.

raising TypeError when statically allocated type subclasses dynamically
allocated type

and socket open until the garbage collector cleans them up.  Patch by
Martin Panter.

Also renames a local to avoid warnings about shadowing