[PATCH] Fix tzfile.c

[Roland McGrath]

> Still, I wonder if it is a good idea to fopen /etc/localtime every time
> strfime, strftime_l or mktime is called or if it wouldn't be enough to
> use the old behaviour of tzset (where if $TZ is unset and was previously
> unset too, nothing will happen) when called from these functions and
> only do the slow path if tzset () is called by the user program.

This is why tzset exists.  I don't thik mktime et al ought to be rechecking
this.