Call thread.join() on threads to prevent the "dangling threads"
warning.

* Remove Setup.config
* Always define WITH_THREAD for compatibility.

Make also minor PEP8 coding style fixes on modified imports.

Thanks to Georg Brandl for the patch.

eliminate all internal uses of overridden methods.

Mark Dickinson.

self-contained, this change facilitates maintenance and the Python version
can be easily imported for experimentation.

This changeset also includes cleanup allowed by this behavior change.

Decimal.quantize() method in the Python version.  It had never been
present in the C version.

This fixes running test_decimal in verbose mode on Windows,
which I broke in issue #19572.

   _decimal:

      o Make all "mpd_t to C integer" conversion functions available in both the
        64-bit and the 32-bit versions.

      o Make all mixed mpd_t/C integer arithmetic functions available in the
        32-bit version.

      o Better handling of __STDC_LIMIT_MACROS for C++ users.

      o Add struct tags (at the request of C++ users).

2) Check for libmpdec.so.2 if --with-system-libmpdec is used.

error messages and comments.

character in _decimal.c.

as reported by Serhiy Storchaka and Matthew Barnett.

InvalidOperation if the format specification (width, prec) exceeds the internal
limits of libmpdec.

and pickling compatibility.

supports all None default values present in decimal.py. These values were
largely undocumented.

from a Decimal argument.

locale, so an additional check is required.