attempted explanation of rsync's symbolic-link handling.

local address is specified, then try all addrinfo records for it.

problems with initialization.

Change the algorithm from trying to open an inbound socket with
getaddrinfo: keep trying suggested addresses until we find one on
which we can both get a socket and bind.  Not convinced this is the
best, but it's probably better.

distributions: we were failing to define HAVE_INET_NTOP, so our
prototype in rsync.h came through.

Also rerun autoheader, and have comment for HAVE_SOCKADDR_STORAGE.

I think this document needs to be reworked to better explain how to
use rsync, but not right now.

initalize the global_opts.af_hint to AF_INET or systems such as Linux that
have a native getaddrinfo() because they support IPv6 will attempt to
create IPv6 sockets.  This brings up a problem with the new global_opts
structure; in order to initialize them to a value other than 0, we need to
explicitly initialize them all in an order that matches the order in
rsync.h.  I think that's more inconvenient & error prone than keeping
global variables.

getaddrinfo(), but only if a corresponding call to socket() returned one of
three *NOSUPPORT errno codes.  A Redhat 6.2 system was observed returning
EINVAL instead so it never went on to try IPv4.  This update adds EINVAL to
the list.  Question: why not always continue through the list regardless of
what errno is?

using the last return code?

copied at all.

getting corrupt output when listing more than one symlink.

picked this up -- quite neat.

isomorphic to sa_family etc from a struct sockaddr, not what they're
called.  On some platforms they seem not to be called ss_family.
Rather than guess, we will try casting to a sockaddr and looking
through that -- I think this is what the RFC intends.

sockaddr_storage is not defined, then supply our own definition that
will hopefully satisfy RFC2553 but also compile on all supported
platforms.

Thankyou to YOSHIFUJI Hideaki, SUMIKAWA Munechika and Jun-ichiro
"itojun" Hagino.