[tz] [PROPOSED] Remove old Y2K code

[Paul Eggert]

On 06/13/2017 12:59 PM, Clive D.W. Feather wrote:
> Better is to have, in the code:
>
> #ifdef DEPRECATE_TWO_DIGIT_YEARS
> #undef DEPRECATE_TWO_DIGIT_YEARS

I prefer the style where the builder uses -D to specify a value, and 
where the code defines a default if -D is not used. This is what's done 
for HAVE_LINK, NETBSD_INSPIRED, USG_COMPAT, etc.