Issue #26516:
* Add PYTHONMALLOC environment variable to set the Python memory
allocators and/or install debug hooks.
* PyMem_SetupDebugHooks() can now also be used on Python compiled in release
mode.
* The PYTHONMALLOCSTATS environment variable can now also be used on Python
compiled in release mode. It now has no effect if set to an empty string.
* In debug mode, debug hooks are now also installed on Python memory allocators
when Python is configured without pymalloc.
Issue #26154: Add a new private _PyThreadState_UncheckedGet() function which
gets the current thread state, but don't call Py_FatalError() if it is NULL.
Python 3.5.1 removed the _PyThreadState_Current symbol from the Python C API to
no more expose complex and private atomic types. Atomic types depends on the
compiler or can even depend on compiler options. The new function
_PyThreadState_UncheckedGet() allows to get the variable value without having
to care of the exact implementation of atomic types.
Changes:
* Replace direct usage of the _PyThreadState_Current variable with a call to
_PyThreadState_UncheckedGet().
* In pystate.c, replace direct usage of the _PyThreadState_Current variable
with the PyThreadState_GET() macro for readability.
* Document also PyThreadState_Get() in pystate.h
Issue #25274: sys.setrecursionlimit() now raises a RecursionError if the new
recursion limit is too low depending at the current recursion depth. Modify
also the "lower-water mark" formula to make it monotonic. This mark is used to
decide when the overflowed flag of the thread state is reset.
