Reflect latest interface changes; return 0 on success and -1 on error.

sysdeps/linux/msg_limits.c

@@ -38,6 +38,8 @@ int
 glibtop_init_msg_limits_s (glibtop *server)
 {
 	server->sysdeps.msg_limits = _glibtop_sysdeps_msg_limits;
+
+	return 0;
 }
 
 /* Provides information about sysv ipc limits. */
@@ -62,4 +64,6 @@ glibtop_get_msg_limits_s (glibtop *server, glibtop_msg_limits *buf)
 	buf->msgmni = msginfo.msgmni;
 	buf->msgssz = msginfo.msgssz;
 	buf->msgtql = msginfo.msgtql;
+
+	return 0;
 }