cleanup&refactor sock.c a bit, change definition for client add/remove functions

server/clients.h

@@ -1,6 +1,8 @@
-/*
- * client.h
- * This file is part of LCDd, the lcdproc server.
+/** \file clients.h
+ * Manage the list of clients that are connected.
+ */
+
+/* This file is part of LCDd, the lcdproc server.
  *
  * This file is released under the GNU General Public License. Refer to the
  * COPYING file distributed with this package.
@@ -21,9 +23,9 @@
 int clients_init(void);
 int clients_shutdown(void);
 
-/* Add/remove clients (return -1 for error) */
-int clients_add_client(Client *c);
-int clients_remove_client(Client *c);
+/* Add/remove clients (return NULL for error) */
+Client *clients_add_client(Client *c);
+Client *clients_remove_client(Client *c);
 
 /* List functions */
 Client *clients_getfirst(void);