tzdata and tzcode back port request

Please backport these changes from master to Fido and Dizzy.

tzcode: update to 2015g
931dda4d9adbefa68b8e6e9796d55a9e3d2bfcee

tzdata: update to 2015g
a0e7311b207e6ea156c89c22388695192ba57f43

and possible

tzdata: reinstate changes reverted in 2014c upgrade 402723ead0b07255497bc137327f2aac0f6c74b0

Fido is at rev 'd' so you may want to backport 'e' or just jump to 'g'

dizzy is at 'b'.. who is maintaining that ; )

- Armin