* leapseconds.awk: Update the IERS's full name.
Be less enthusiastic about Shanks and clarify UT vs UTC.

* africa, asia, australasia, backzone, europe, northamerica:
* southamerica, tz-link.htm: Be less enthusiastic about Shanks.
* tz-link.htm: Be clearer about UT vs UTC.
* NEWS: Document this.
Move out-of-scope UTC+3 African zones to 'backzone'.

* africa (Africa/Addis_Ababa, Africa/Asmara, Africa/Dar_es_Salaam)
(Africa/Djibouti, Africa/Kampala, Africa/Mogadishu, Indian/Antananarivo)
(Indian/Comoro, Indian/Mayotte):
Change these from zones to links to Africa/Nairobi.
* backzone: Move the old data here.
* checktab.awk (tztab): Remove special cases for these zones.
* NEWS: Document the above.
* europe: Add Countess Markievicz's take on the Summer Time Act, 1916.