UBIFS: media format changes

[Artem Bityutskiy]

Hi all,

as we have announced UBIFS, it is good idea to notify people
who may try to use it about media format changes.

We now store nanoseconds in [amc]time in inodes, not just seconds,
and the latest UBIFS is incompatible to the previous versions,
which means it will refuse mounting older images.

You should also update mkfs.ubifs utility.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)