Attached is a cleanup of the main loops in sys_msgrcv and sys_msgsnd, based on
ipc_lock_by_ptr().  Most backward gotos are gone, instead normal "for(;;)"
loops until a suitable message is found.

Description:

- General cleanup of sys_msgrcv and sys_msgsnd: the function were too
  convoluted.

- Enable lockless receive, update comments.

- Use ipc_getref for sys_msgsnd(), it's better than rechecking that the
  msqid is still valid.
Signed-Off-By: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>