Issue #14339: Improve speed of bin, oct and hex builtins.  Patch by Serhiy Storchaka (with minor modifications).

as found in sys.modules and not as what the loader returns (even
though it is required to by PEP 302).

importlib.test.import_ using builtins.__import__() instead of just the
relative import tests.

extension modules.

in Python/dynload_shlibs.c.

This should fix the remaining importlib test failure on Windows.
Support in AIX and HP-UX will be in a separate checkin.

this is more readable.

  1) Rename _mpd_qbarrett_divmod into _mpd_base_ndivmod: The function is
     only marginally related to either Barrett's algorithm or to the version
     in Hasselstrom's paper.

  2) In places where the proof assumes exact operations, use new versions of
     add/sub/multiply that set NaN/Invalid_operation if this condition is
     not met. According to the proof this cannot happen, so this should be
     regarded as an extra safety net.

  3) Raise Division_impossible for operands with a number of digits greater
     than MPD_MAX_PREC. This facilitates the audit of the function and can
     practically only occur in the 32-bit version under conditions where
     a MemoryError is already imminent.

  4) Use _mpd_qmul() in places where the result can exceed MPD_MAX_PREC in
     a well defined manner.

  5) Test for mpd_isspecial(qq) in a place where the addition of one
     can theoretically trigger a Malloc_error.

  6) Remove redundant code in _mpd_qdivmod().

  7) Add many comments.

tokenizer.detect_encoding() (when available).

#14629 changed the message.

the file suffix's case into account, even when doing a case-sensitive
import.

sure finders from importlib are used instead of _frozen_importlib.

if the first two lines have non-UTF-8 characters without an encoding declaration.

Issue #14308: Fix an exception when a dummy thread is in the threading module's active list after a fork().

Issue #14308: Fix an exception when a "dummy" thread is in the threading module's active list after a fork().

Patch by Stefan Behnel.

It is now possible to use a custom type for the __builtins__ namespace, instead
of a dict. It can be used for sandboxing for example.  Raise also a NameError
instead of ImportError if __build_class__ name if not found in __builtins__.

_multiprocessing.win32 modules now live in a single module "_winapi".
Patch by sbt.

   in order to understand the algorithm anyway.

2) v->exp == -v->digits may be assumed.

3) Fix comment (v always shares data with a).

rightfully states that an mpd_t with a coefficient flagged as MPD_CONST_DATA
must not be in the position of the result operand. In this particular case
several assumptions guarantee that a resize will never occur in all possible
code paths, which was the reason for using MPD_CONST_DATA and saving an
instruction by omitting the initialization of tmp.alloc.

For readability, tmp is now flagged as MPD_STATIC_DATA and tmp.alloc
is initialized.