[LEAPSECS] stale leap second information

[Tom Van Baak]

> To be fair, and here I declare myself as an ex-member of the SOFA
> board, the software is clearly labelled "2001-03-31 release".  That
> page is no longer even accessible from the SOFA home page where the
> latest release is dated 2014-10-07.
> 
> Regards,
> Mark Calabretta

Hi Mark,

I understand, but it's one of the first hits on google for some searches, regardless of how the home page is organized.

A suggestion -- any hardcoded leap second tables should give an expiration date along with instructions for updating the table.

Add that to the growing list of leap second best practices.

/tvb