This makes memdie a TIF_MEMDIE.

memdie will not be modified by the current task, so it cannot be a
PF_MEMDIE but it must be a TIF_MEMDIE.
Signed-off-by: Andrea Arcangeli <andrea@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>