add support for POSIX message queues, except mq_notify

src/mq/mq_timedreceive.c

@@ -0,0 +1,7 @@
+#include <mqueue.h>
+#include "syscall.h"
+
+ssize_t mq_timedreceive(mqd_t mqd, char *msg, size_t len, unsigned *prio, const struct timespec *at)
+{
+	return syscall(SYS_mq_timedreceive, mqd, msg, len, prio, at);
+}