pkt.u64: fix result type
pack_u16, pack_u32: cpdef
TX,BLOCK.{raw,name}: made readonly
TX.unpack: set self.name
pprint_script: useful for tx.dump()
verifying_machine.check_sig: remove debug print
eval_script: return check_sig result
pprint_unit_tests: test pprint
remove debug prints
pull in pprint_script, hexify
VerifyError: new
remove old hackish script parse/unparse code
chain-walking generators: chain_gen, longest, db_gen
txmap: start on a 'live money' db