[parrot/parrot] bc6c41: mark unused stuff with UNUSED()

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/parrot/parrot
  Commit: bc6c413e610709338014379ac3c29f29b5432e85
      https://github.com/parrot/parrot/commit/bc6c413e610709338014379ac3c29f29b5432e85
  Author: Andy Lester <andy at petdance.com>
  Date:   2012-03-25 (Sun, 25 Mar 2012)

  Changed paths:
    M src/pmc/null.pmc

  Log Message:
  -----------
  mark unused stuff with UNUSED()