[tz] [PROPOSED] Remove old Y2K code

[Zefram]

Clive D.W. Feather wrote:
>#ifdef DEPRECATE_TWO_DIGIT_YEARS
>#undef DEPRECATE_TWO_DIGIT_YEARS
>#define DEPRECATE_TWO_DIGIT_YEARS true
>#else
>#define DEPRECATE_TWO_DIGIT_YEARS false
>#endif
>
>so that it can't be misdefined.

That would be liable to encourage someone to put
-DDEPRECATE_TWO_DIGIT_YEARS=false on the command line, which it would
then handle poorly.  Pick one convention or the other for that symbol;
if you want to use the other convention internally, apply it to a
different symbol.

-zefram