- make abday, day, abmon, mon, am_pm output quoting match linux
- workaround localeconv() issue for mon_grouping and grouping (PR172215)
- for other values not available in default locale, output -1 instead of
127 (CHAR_MAX) as returned by localeconv()
With these changes, output of `locale` and `locale -k` for all keywords
specified by POSIX exactly matches the linux one.
PR: 237752
Reviewed by: bapt
Differential Revision: https://reviews.freebsd.org/D21599
