Since svn r1475/git 5b6099e8 in tor-0.0.6, we have responded to an
exhaustion of all 65535 stream IDs on a circuit by marking that
circuit for close.  That's not the right response.  Instead, we
should mark the circuit as "too dirty for new circuits".

Of course in reality this isn't really right either.  If somebody
has managed to cram 65535 streams onto a circuit, the circuit is
probably not going to work well for any of those streams, so maybe
we should be limiting the number of streams on an origin circuit
concurrently.

Also, closing the stream in this case is probably the wrong thing to
do as well, but fixing that can also wait.