utf-8 encode for date string

[eightbit]

in korean, date format is like this:

2004-12-26 오전 10:08:20 ('오전' means 'forenoon')

date string have 'forenoon' and 'afternoon'. so, date string should be encoded with 'utf-8'

in addition, korean charset name is 'euc-kr' it can use like this in python language:

util.to_utf8(strdate, 'euc-kr')

'euc-kr' can replace with default charset value in trac.ini. i think this code will not affect to other charset.

[cmlenz]

Duplicate of #1081.