Introduce new --local-service=host parameter

Similar to local-service, but more strict. Listen only on localhost
unless other interface is specified. Has no effect when interface is
provided explicitly. I had multiple bugs fillen on Fedora, because I have
changed default configuration to:

interface=lo
bind-interfaces

People just adding configuration parts to /etc/dnsmasq.d or appending to
existing configuration often fail to see some defaults are already there.
Give them auto-ignored configuration as smart default.

Signed-off-by: Petr Menšík <pemensik@redhat.com>

Do not add a new parameter on command line. Instead add just parameter
for behaviour modification of existing local-service option. Now it
accepts two optional values:
- net: exactly the same as before
- host: bind only to lo interface, do not listen on any other addresses
  than loopback.

src/dnsmasq.c

@@ -868,6 +868,8 @@ int main (int argc, char **argv)
 
       if (option_bool(OPT_LOCAL_SERVICE))
 	my_syslog(LOG_INFO, _("DNS service limited to local subnets"));
+      else if (option_bool(OPT_LOCALHOST_SERVICE))
+	my_syslog(LOG_INFO, _("DNS service limited to localhost"));
     }
   
   my_syslog(LOG_INFO, _("compile time options: %s"), compile_opts);