* binarin/erts/fix-epmd-systemd-notifications/PR-999/OTP-13493:
  Don't send unasked for systemd notifications

* henrik/update-copyrightyear:
  update copyright-year

Suppose we have some erlang system that uses systemd unit with
Type=notify - so this should send startup confirmation itself. But if
systemd-enabled epmd will be started as a first step of that system
startup, empd startup confirmation will be misinterpeted by systemd. And
our erlang service will be considered 'ready' to early. Also this will
interefere with systemd MAINPID detection: systemd will be monitoring
`epmd` process instead of `beam` one.

For example, rabbitmq works around this issue by starting epmd using
separate short-lived beam process, with NOTIFY_SOCKET environment
variable reset - only in this way we could be sure that epmd will not
interfere with rabbit startup sequence.

This patch disables indiscriminate confirmation sending, and does it
only when it was explicitly asked to do so.

Patch from end of PR 864
Fixes problem reported in the PR by jeckersb

In this error case, a negative file descriptor is now saved at
listensock[i], which leads to a buffer overflow later on at
https://github.com/msantos/otp/blob/epmd-IPv6-node-reg2/erts/epmd/src/epmd_srv.c#L498
when calling FD_ISSET(listensock[i],&read_mask).

To reproduce this:

    Completely disable IPv6 with ipv6.disable=1 on the kernel command line
    Build with fortified code (RHEL/CentOS default): CFLAGS='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -fno-strict-aliasing'

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.