[tz] Buggy %z behaviour in strftime

[Paul Eggert]

On 7/18/22 10:30, Robert Elz via tz wrote:
> So, tm_isdst is all that is ever need to select one of those.

Good point.

Still, the C standard (which doesn't mention TZ) should not impose a 
at-most-two-offsets requirement, since that's not how many C 
implementations actually behave. And once we get the C standard fixed 
POSIX will follow, and this should allow the common behavior when TZ has 
a value like "America/Los_Angeles" or ":America/Los_Angeles" that uses 
our extension to POSIX.