Merge r307359 from stable/10:

Merge r307359 from stable/10:

    Incorporate a change from OpenBSD by millert@OpenBSD.org

    Don't warn about valid time zone abbreviations.  POSIX
    through 2000 says that an abbreviation cannot start with ':', and
    cannot contain ',', '-', '+', NUL, or a digit.  POSIX from 2001
    on changes this rule to say that an abbreviation can contain only
    '-', '+', and alphanumeric characters from the portable character
    set in the current locale.  To be portable to both sets of rules,
    an abbreviation must therefore use only ASCII letters."  Adapted
    from tzcode2015f.

Errata Notice:	EN-16:19.tzcode
Submitted by:	bapt
Approved by:	so

git-svn-id: svn://svn.freebsd.org/base/releng/10.3@309572 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f