bpo-34523, bpo-35290: C locale coercion now resets the Python
internal "force ASCII" mode. This change fix the filesystem encoding
on FreeBSD CURRENT, which has a new "C.UTF-8" locale, when
the UTF-8 mode is disabled.
Add _Py_ResetForceASCII(): _Py_SetLocaleFromEnv() now calls it.
locale.localeconv() now sets temporarily the LC_CTYPE locale to the
LC_MONETARY locale if the two locales are different and monetary
strings are non-ASCII. This temporary change affects other threads.
Changes:
* locale.localeconv() can now set LC_CTYPE to LC_MONETARY to decode
monetary fields.
* Add LocaleInfo.grouping_buffer: copy localeconv() grouping string
since it can be replaced anytime if a different thread calls
localeconv().
* _Py_GetLocaleconvNumeric() now requires a "struct lconv *"
structure, so locale.localeconv() now longer calls localeconv()
twice. Moreover, the function now requires all arguments to be
non-NULL.
* Rename STATIC_LOCALE_INFO_INIT to LocaleInfo_STATIC_INIT.
* Move _Py_GetLocaleconvNumeric() definition from fileutils.h
to pycore_fileutils.h. pycore_fileutils.h now includes locale.h.
* The _locale module is now built with Py_BUILD_CORE defined.