Allow hostnames in bridge configuration lines when used with PTs
When using pluggable transports, maybe it should be allowed to have bridge addresses be hostnames, and pass those bridge hostnames to the PT over SOCKS.
Possibly not all PTs want to support this. If that's the case, we'll need a way for the PTs that want it to advertise their support.
This came out of our discussion of legacy/trac#10801 (moved).