[rfc] bencode unicode strings

[Alexander Belchenko]

For QBzr needs I need to implement support for bencoding unicode 
strings. Standard bencode uses strings in the stream as byte streams.

Because Qt internally works with pure unicode (not utf-8 as gtk) then I 
have to encode strings to utf-8 manually. I want bencode to handle this 
for me.

I'm not sure how it handled in revision serializer and does it makes 
sense to have such support in the core?