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

[Paul Eggert]

While testing some code I discovered that the tz strftime week numbers
are incompatible with the %V week numbers generated by Solaris 2.5.1 strftime
and with the GNU C Library strftime.  I don't know what the correct
definition of week numbers is (and I don't particularly want to know :-)
but I thought I should report the problem, since it's two against one.
#defining XPG4_1994_04_09 fixes some but not all of the discrepancies.

Here are all examples of discrepancies from 1994 through 1998.  Each
column contains the output of strftime applied to "%U %V %W" for the
given date.  In the cases marked `*', #defining XPG4_1994_04_09 didn't
remove the discrepancy.

		Solaris
date		& glibc		tz		tz with XPG4_1994_04_09
1994-01-01	00 53 00	00 52 00	00 53 00
1994-01-02	01 53 00	01 52 00	01 53 00
1995-01-01	01 53 00	01 52 00	01 53 00
1996-12-30	52 53 53	52 01 53	52 01 53*
1996-12-31	52 53 53	52 01 53	52 01 53*
1997-12-29	52 53 52	52 01 52	52 01 52*
1997-12-30	52 53 52	52 01 52	52 01 52*
1997-12-31	52 53 52	52 01 52	52 01 52*

While we're on the subject, perhaps XPG4 behavior should be the default,
with non-standard behavior being an option.