This function has a nasty API, since whether or not it invokes the
resolver depends on whether one of its arguments is NULL. That's a
good way for accidents to happen.
This patch incidentally makes tor-resolve support socks hosts on
IPv6.
These are now combined into an inaddr.[ch], since their purpose is
to implement functions for struct in_addr and struct in6_addr.
The definitions for in6_addr and its allies are now in a separate
header, inaddr_st.h.
Closes ticket 26532.
