src/types.c: Cope with multiple address families when dereferencing.

src/types.c: Cope with multiple address families when dereferencing.

The pap_findaddrs/pap_hostaddr machinery is improved to cope with
multiple address families.  First of all, we must find out which
families are wanted, using addr_rrtypes.  Then we keep track of which
address types are satisfied from the additional section, during
pap_findaddrs, and submit addr subqueries to look them up.  (We no
longer issue the top-level addr query: we handle the individual
subqueries ourselves, because we have to merge the results onto the
existing vector of addresses.)

Signed-off-by: Mark Wooding <mdw@distorted.org.uk>