Specifically, split compare_tor_addr_to_addr_policy() from a loop with a bunch
of complicated ifs inside into some ifs, each with a simple loop.  Rearrange
router_find_exact_exit_enclave() to run a little faster.  Bizarrely,
router_policy_rejects_all() shows up on oprofile, so precalculate it per
routerinfo.

svn:r17802