* net/tramp-gw.el (tramp-gw-open-connection): Suppress traces in
wrong debug buffer.
(tramp-gw-open-connection): Set process coding system 'binary.
(tramp-gw-open-network-stream): Handle HTTP error 403.

* net/tramp-sh.el (tramp-compute-multi-hops): Suppress traces in
wrong debug buffer.
(tramp-maybe-open-connection): Set connection property "gateway".

* net/tramp.el (tramp-error-with-buffer): Call `message' properly.
(tramp-accept-process-output): Use nil as argument for
`accept-process-output', when there is a gateway prepended.