So if there are no HTLCs, and the receiver can't spend anyway, don't
sign. This has the added benefit that no two signed commitment
transactions will ever be identical (the revocation preimage changes).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We no longer need it anywhere. This simplifies things to the point where
we might as well just not include dust outputs as we go, rather than
explicitly removing them, which gets rid of remove_dust.c as well.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>