Add a missing 00-INDEX file for Documentation/vm/

This patch adds a 00-INDEX file to Documentation/vm/

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Acked-by: Rob Landley <rob@landley.net>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>