tz strftime %V week numbers are incompatible with Solaris, GNU

[Arthur David Olson]

The current strftime code is supposed to deliver up ISO 8601 week numbers
when "%V" is used; it also delivers up ISO 8601 year numbers--either two or
four digits worth--with "%g" and "%G". (The ISO 8601 year may be different from
the calendar year).

So far as I know, the code's current behavior matches what ISO 8601 calls for.
XPG4 (as of 1994-04-09) explicitly (and presumably erroneously) called for
delivering "53" as the week number in some circumstances; defining
"XPG4_1994_04_09" buys this behavior.

I'm eager to continue delivering ISO-8601-style numbers as the default
behavior.

				--ado