serve: use chunked encoding in hgweb responses 'hg serve' used to close connections when sending a response with unknown length ... such as a bundle or archive. Now chunked encoding will be used for responses with unknown length, and the connection do thus not have to be closed to indicate the end of the response. Chunked encoding is only used if the length is unknown, if the connection wouldn't be closed for other reasons, AND if it is a HTTP 1.1 request. This will not benefit other users of hgweb ... but it can serve as an example that it can be done.

serve: remove connection close hack for Python 2.3 Introduced in 276de216d2c5 and no longer needed - BaseHTTPServer handles connection closing just fine if we don't mess with its internals.

hgweb: pass the actual response body to request.response, not just the length This makes it less likely to send a response that doesn't match Content-Length.