Stuff that doesn't work yet in IPv6 patch

The IPv6 patch seems to still be a few bricks shy of a load. Grepping
for places that handle AF_INET but not AF_INET6 revealed these
unimplemented features:

1. IDENT authorization. Fails if either local or remote address is IPv6.

2. SSL. Postmaster allows SSL for AF_INET but not AF_INET6.

3. Client address display in backend's ps display seems to be v4 only.

4. pgstat code can only bind to 127.0.0.1 (v4 loopback). On a v6-only
machine this would not exist, would it?

regards, tom lane