ipc: restore MSGPOOL original value

When posting:

	[PATCH 1/8] Scaling msgmni to the amount of lowmem

(see http://article.gmane.org/gmane.linux.kernel/637849/

) I changed the
MSGPOOL value to make it fit what is said in the man pages (i.e.  a size
in bytes).

But Michael Kerrisk rightly complained that this change could affect the
ABI.  So I'm posting this patch to make MSGPOOL expressed back in Kbytes.
Michael, on his side, has fixed the man page.

Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Pierre Peiffer <peifferp@gmail.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Acked-by: Michael Kerrisk <mtk.manpages@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>