[PATCH 0 of 2 stable] notify: fix ellipsis of long multi-byte subject (issue2564)

[Yuya Nishihara]

Hi,

These patches fix notify extension not to break multi-byte text
on email subject.

For details, please see
http://mercurial.selenic.com/bts/issue2564

Patches:
1. use util.ellipsis()
2. make util.ellipsis() multi-byte aware

Yuya,