Fix bug reported by Xucaen (sort-of):

Check the user's 'M' restriction before allowing them to send netmail and throw
an error if they're not allowed.
The actual bug reported was that the global setting in SCFG->Networks->Internet
->Allow Sending of E-Mail wasn't being followed in the old/legacy Web GUI,
and that's still the case because the scfg_t.inetmail_misc value isn't
(currently) exposed via JavaScript even though the bit-flag values (NMAIL_*)
are defined in sbbsdefs.js - whoops, just an oversight.

web/root/msgs/savemsg.ssjs

@@ -25,9 +25,11 @@ if(sub!='mail')  {
 }
 else {
 	hdrs.to_net_type=netaddr_type(http_request.query.to);
-	if(hdrs.to_net_type!=NET_NONE)
+	if(hdrs.to_net_type!=NET_NONE) {
+		if(user.security.restrictions&UFLAG_M)
+			error("You do not have permission to send netmail");
 		hdrs.to_net_addr=http_request.query.to;
-	else {
+	} else {
 		var usr=system.matchuser(http_request.query.to);
 		if(usr!=0)
 			hdrs.to_ext=usr;