Suggested by @m-schmook, I realized that if we append it later I'll
never get it right: I expect parameters min and max, not max and min!
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: Protocol: you can now alter the `htlc_minimum_msat` and `htlc_maximum_msat` your node advertizes.