Remove exported function create_server_list()

The guts of this function doesn't need to be in server.c - it only uses extern server functions so it
makes sense just to move it into the body of function_servers(), the only caller.

That means it's no longer accessible for loadable modules, but it isn't much use for them anyway.  They
can always directly access the server list if they need that info.

(Requires rolling the module table version).

source/functions.c

@@ -1903,7 +1903,29 @@ BUILT_IN_FUNCTION(function_channels, input)
 
 BUILT_IN_FUNCTION(function_servers, input)
 {
-	RETURN_MSTR(create_server_list(input));		/* DONT USE RETURN_STR HERE! */
+	const int n_servers = server_list_size();
+	int	i;
+	int	do_read = 0;
+	char *value = NULL;
+
+	if (input && *input == '1')
+		do_read = 1;
+
+	for (i = 0; i < n_servers; i++)
+	{
+		if (do_read)
+		{
+			if (is_server_connected(i))
+				m_s3cat(&value, " ", ltoa(i));
+		}
+		else
+		{
+			if (is_server_open(i))
+				m_s3cat(&value, " ", get_server_itsname(i));
+		}
+	}
+
+	RETURN_MSTR(value);
 }
 
 BUILT_IN_FUNCTION(function_pid, input)