compiler.rb: Switch to modern facts

[bastelfreak]

All of those are available at least since Facter 3.

[ekohl]

I'd also take the chance to look at a new structured fact called puppetserver and add all the values in there.

You can probably be smart and align the facts to networking facts:

# Copy networking facts if available
['fqdn', 'ip', 'ip6'].each do |var|
  if (value = Facter.value("networking.#{var}"))
    @server_facts[var] = value
  end
end