SPDY: consistently handle control frames with unknown type. The SPDY draft 2 specification requires that if an endpoint receives a control frame for a type it does not recognize, it must ignore the frame. But the 3 and 3.1 drafts don't seem to declare any behavior for such case. Then sticking with the previous draft in this matter looks to be right. But previously, only 8 least significant bits of the type field were parsed while the rest of 16 bits of the field were checked against zero. Though there are no known frame types bigger than 255, this resulted in inconsistency in handling of such frames: they were not recognized as valid frames at all, and the connection was closed.

scgi_param  REQUEST_METHOD     $request_method;
scgi_param  REQUEST_URI        $request_uri;
scgi_param  QUERY_STRING       $query_string;
scgi_param  CONTENT_TYPE       $content_type;

scgi_param  DOCUMENT_URI       $document_uri;
scgi_param  DOCUMENT_ROOT      $document_root;
scgi_param  SCGI               1;
scgi_param  SERVER_PROTOCOL    $server_protocol;
scgi_param  HTTPS              $https if_not_empty;

scgi_param  REMOTE_ADDR        $remote_addr;
scgi_param  REMOTE_PORT        $remote_port;
scgi_param  SERVER_PORT        $server_port;
scgi_param  SERVER_NAME        $server_name;