[PATCH] Add the rules about the -stable kernel releases to the Documentation directory

This was the last agreed upon set of rules, it's probably time we actually add
them to the kernel tree to make them "official".

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>