* msantos/epmd-IPv6-node-reg2/PR-864/OTP-13364:
  epmd: support IPv6 node registration

Fix mistakes found by 'xmllint'.

Allow IPv6 nodes to register with and query epmd. On systems with
IPv6 support:

* epmd listens on both the IPv4 and IPv6 ANY or loopback sockets

* the epmd cli client connects to epmd over the IPv6 loopback

* distributed nodes started with "-proto_dist inet6_tcp" will register
  with epmd over IPv6

To work on IPv6 capable systems that have IPv6 support disabled,
epmd ignores errors opening the socket if the protocol is not
supported. Similarly, the epmd client will fall back to IPv4 if the IPv6
socket is not available.

Update the minimum supported version of Windows to Windows Vista to
support IPv6.

192c4a80c broke the build on at least Debian/Hurd and Debian/kFreeBSD,
because it's not linux but still using glibc. To fix it, test for
__GLIBC__ in addition to __linux__.

This reverts commit 192c4a80c7d6fe9949aecb864901c4a3d9549f36.

This breaks on Debian/Hurd, Debian/kFreeBSD, and possibly other
platforms as well. Will be solved differently in a follow-up commit.

To fix conditional selection of the actually available gethostbyname_r
and gethostbyaddr_r, we replace __GLIBC__ with __linux__.  @zenhack
tested this to work with gcc and clang targeting glibc, uclibc, musl,
and bionic.

The proper way to check this is through configure.in.