Bad headers in jsonp-polling, xhr-polling

[SlNPacifist]

jsonp-polling and xhr-polling require encoding parameter in Content-type header (some browsers decode data got with this methods with page's encoding)
Content-length gets corrupted if non-english symbols are sent because it requires number of bytes but string.length returns number of symbols in string.
This issue is fixed in http://github.com/SlNPacifist/Socket.IO-node branch
Buffer.byteLength is used, but Buffer became global object only in node.js v 0.1.103, so after merging with branch that will become the least version needed.

[rauchg]

Fixed