[COMMITED][BZ #16854] Fix recvmmsg comment.

[Ondřej Bílka]

Hi, as recvmmsg returns number of messages received I fixed comment that
said it returns number of bytes. Commited as obvious.

	[BZ #16854]
	* socket/sys/socket.h: Fix typo in comment.

diff --git a/socket/sys/socket.h b/socket/sys/socket.h
index c0f3ee6..95ee26a 100644
--- a/socket/sys/socket.h
+++ b/socket/sys/socket.h
@@ -203,7 +203,7 @@ extern ssize_t recvmsg (int __fd, struct msghdr *__message, int __flags);
 
 #ifdef __USE_GNU
 /* Receive up to VLEN messages as described by VMESSAGES from socket FD.
-   Returns the number of bytes read or -1 for errors.
+   Returns the number of messages received or -1 for errors.
 
    This function is a cancellation point and therefore not marked with
    __THROW.  */