Fix bitcoin's broken merkle tree about hsd HOT 2 CLOSED

RFC7574 is also an option. It looks like it pads the leaves with zero hashes until the amount of leaves reaches the nearest power of two (?). This is nicer than rfc6962 in that all the leaves are guaranteed to be the same depth. Might make dealing with proofs more sane.

Though, if we just wanted the leaves to be the same depth, we could do a combination of both. RFC6962-style, but if the leaves are odd, we pad them with a single zero-hash. This ensures that the odd leaf never gets propagated up. For all levels above the leaves, we propagate the odd hash up.

edit: See also, bittorrent's BEP 0030: http://bittorrent.org/beps/bep_0030.html

from hsd.

Note that changing any of this will also require changing the bip37-style SPV (which we should remove in the future anyway).

from hsd.