[conformal/btcscript] da1fcc: Tighten the check for pay-to-pubkey scripts.

[Dave Collins]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcscript
  Commit: da1fcc6dbd71fd14de90e77ce77895f26383c10f
      
https://github.com/conformal/btcscript/commit/da1fcc6dbd71fd14de90e77ce77895f26383c10f
  Author: Dave Collins <da...@conformal.com>
  Date:   2014-02-21 (Fri, 21 Feb 2014)

  Changed paths:
    M script.go

  Log Message:
  -----------
  Tighten the check for pay-to-pubkey scripts.

This commit tightens the check for a pay-to-pubkey script by ensuring the
length of the pubkey is one of the two valid values of 33 or 65.  This
mirrors the checks in the multisig script type check as well.

ok @owainga