src/liboping.c: Fixed the handling of multiple hosts.

src/liboping.c: Fixed the handling of multiple hosts.

ping_receive_all() used to always pass the first host object to
ping_receive_one() which used that host object to determine the expected
address family. Thus, when pinging v4 and v6 hosts in parallel, some of them
would have never been considered but assumed to be timed out.

While at it, the code has been clarified in regard to matching an ECHO_REPLY
with the appropriate host object.