Added 'reinitialize_command()' -- lets us "push" option values in
  a controlled, safe way; this is a small change to the code, but
  a big change to the Distutils philosophy of passing option values
  around.  The preferred mode is still definitely to "pull" options
  from another command (eg. "install" fetches the base build directory
  from "build"), but it is now feasible to "push" options onto another
  command, when you know what's best for it.  One possible application
  will be a "config" command, which pokes around the system and pushes
  values (eg. include and library directories) onto the "build" command.
Added 'dump_option_dicts()' method (for debugging output).