Relax local FreeBSD restrictions on 3 chars abbrev. name length and %c format

Relax local FreeBSD restrictions on 3 chars abbrev. name length and %c format
since they not allows POSIXly legal locale data. Currently, if relaxed form
POSIXly legal locale data will be used right now, some programs will be broken,
but it means that either locale data or programs must be fixed, not the library.

Introduce non-standard md_order (month/day order) locale field to be used later
via nl_langinfo(). Currently %EF and %Ef emulated using this field, but they
planned for remove in future in favour of nl_langinfo() test field.

Implement %F per POSIX