2 - Relays now process the new "NTor" circuit-level handshake requests
3 with higher priority than the old "TAP" circuit-level handshake
4 requests. We still process some TAP requests to not totally starve
5 0.2.3 clients when NTor becomes popular. A new consensus parameter
6 "NumNTorsPerTAP" lets us tune the balance later if we need to.
7 Implements ticket 9574.