BUG/MEDIUM: mux_h1: Process a new request if we already received it.

BUG/MEDIUM: mux_h1: Process a new request if we already received it.

In h1_detach(), if our input buffer isn't empty, don't just subscribe(), we
may hold a new request, and there's nothing left to read. Instead, call
h1_process() directly, so that a new stream is created.
Failure to do so means if we received the new request to early, the
connecetion will just hang, as it happens when using svn.