[btcsuite/btcd] 9abc2c: txscript: Comment improvements and fixes

[Dave Collins]

  Branch: refs/heads/master
  Home:   https://github.com/btcsuite/btcd
  Commit: 9abc2c0e19eee22048fa7b070b98e543fea42a60
      
https://github.com/btcsuite/btcd/commit/9abc2c0e19eee22048fa7b070b98e543fea42a60
  Author: Dave Collins <da...@conformal.com>
  Date:   2016-02-11 (Thu, 11 Feb 2016)

  Changed paths:
    M txscript/opcode.go

  Log Message:
  -----------
  txscript: Comment improvements and fixes

This commit improves and corrects a few comments in txscript to ensure
they match reality.