[conformal/btcscript] aa3cdb: use fastsha256

[Marco Peereboom]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcscript
  Commit: aa3cdbe7b1d0059c5f01c60595e233a2b40a8463
      
https://github.com/conformal/btcscript/commit/aa3cdbe7b1d0059c5f01c60595e233a2b40a8463
  Author: Marco Peereboom <ma...@conformal.com>
  Date:   2013-11-19 (Tue, 19 Nov 2013)

  Changed paths:
    M opcode.go

  Log Message:
  -----------
  use fastsha256