Reconstruct and merge 4561 leftover code that adds wrappers for address-access functions

In legacy/trac#4561 (moved) we extended Tor to no longer assume that a relay or bridge has exactly one address. That code is written, reviewed, and ready to be merged. But Git master will become 0.2.3.x, and there's no branch for 0.2.4.x branch yet where we could merge this code. This ticket is for merging ln5's bug4561_4 branch once we have an 0.2.4.x branch.