fix drop_signatures for OP_CHECKMULTISIG tx in testnet3

  input_script["OP_0 sig-1 sig-2"] + output_script["sig-1 OP_DROP 2 pub-1 pub-2 2 OP_CHECKMULTISIG"]

  where sig-1 is hash-type: single
fix OP_CODESEPARATOR in signature_hash_for_input

  input_script["sig-1"] + output_script["OP_CODESEPARATOR pub-1 OP_CHECKSIG"]
another fix for OP_CODESEPARATOR in signature_hash_for_input

  input_script["sig-1"] + output_script["pub-1 OP_CODESEPARATOR OP_CHECKSIG"]
Merge branch 'master' of https://github.com/lian/bitcoin-ruby