[tz] 2014g soon

It's time for a new tz release: we have one change to near-future data (for the Turks & Caicos) that should go out sooner rather than later, and there've been several changes to the code as well. To help simplify reviewing I've pushed an integrated version of the proposed changes to <https://github.com/eggert/tz>, and you can read the news here: https://github.com/eggert/tz/blob/master/NEWS