Changes needed for checking for unreachable code (& implicit returns):   * Return 3 items (including code index) from nextOpInfo   * Change returnValues[] (& raiseValues[]) to be a list of:       (line, stackItem, codeIndex)   * Add handler for RAISE_VARARGS op
Changes needed for checking for unreachable code (& implicit returns):
  * Return 3 items (including code index) from nextOpInfo
  * Change returnValues[] (& raiseValues[]) to be a list of:
      (line, stackItem, codeIndex)
  * Add handler for RAISE_VARARGS op

Lots o' cleanup:
  * Remove lastReturnLabel, maxLabel, and returns, these can all be calculated
  * Add raiseValues list for checking unused code later
  * Change getNextOp() -> popNextOp() to distinguish better from nextOpInfo()
    which doesn't remove the op

FIXME: what to do w/removeBranch(), remove it?

smspillaz/pychecker,smspillaz/pychecker,smspillaz/pychecker