A pretty serious oversight :) this was not noticed because I was
simultaneously dealing with a serious tcp connection bug in rustc,
and I had thought bitcoind's angry disconnects were a further
symptom of that.
This is a massive simplification, fixes a couple endianness bugs (though
not all of them I don't think), should give a speedup, gets rid of the
`serialize_iter` crap.
I think this is what I want to do for everything json-visible...perhaps
I will not be able to keep the macro for it though, since there are
some clever variations on it (e.g. blocks should have their header's
hash as a field, txes should appear as txids unless vebose output is
requested, etc.)
It is now visible that EOF (i.e. peer hung up) is interpreted
as a message decode error. Probably what we want to do is reset
the connection on any error. TODO
We get a speed up (~5%) and memory savings (~10%) on initial sync from
using a HashMap, though it's hard to tell precisely how much savings
because it's quite nonlinear.
I haven't tested de/serialization. Some work needs to be done there to
split up the UTXO set since it takes forever to saveload.
We were conflicting with the Rust stdlib trait Hash, which is used
by various datastructures which need a general hash. Also implement
Hash for Sha256dHash so that we can use bitcoin hashes as keys for
such data structures.