And support for varnish 6 and ipv6 addresses

Problem/Motivation

Varnish is now on version 6, and ipv6 is slowly but surely adopted, now forming more than a third of the addresses.

Steps to reproduce

Proposed resolution

For ipv6, inside function _varnish_terminal_run

  foreach ($terminals as $terminal) {
  
    //list($server, $port) = explode(':', $terminal);
    //$client = socket_create(AF_INET, SOCK_STREAM, getprotobyname('tcp'));

    $server = substr($terminal,1,strrpos($terminal,":")-2);
    $port = substr($terminal,strrpos($terminal,":")+1);
    dpm($terminal." ".strrpos($terminal,":")." ".$server.' '.$port, 'terminal');
    $client = socket_create(AF_INET6, SOCK_STREAM, getprotobyname('tcp'));

This is just an example of code but user should have the option to choose between ipv4 and ipv6. Anyway after this change, I was able to connect to varnish and write, but not to read. I suppose this is a problem linked to Varnish 6 adaptation.

Remaining tasks

User interface changes

API changes

Data model changes