Ticket #542 (defect)

From http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2:

"Multiple message-header fields with the same field-name MAY be present in a message if and only if the entire field-value for that header field is defined as a comma-separated list [i.e., #(values)]. It MUST be possible to combine the multiple header fields into one "field-name: field-value" pair, without changing the semantics of the message, by appending each subsequent field-value to the first, each separated by a comma."

The WSGI spec doesn't allow for multiple headers, so the HTTP server should concatenate them into a single header for WSGI transport.