How do you get the RMS structures out from "underneath" C?

  Under DEC C, use the "acc" callback on the open() call to get access
  to the FAB and RAB.

  Under VAX C, use the _fstat call.  _fstat() takes four arguments,
  a file descriptor, a pointer to a pointer to a FAB, a pointer to a 
  pointer to a NAM, and a pointer to a pointer to a RAB.  The latter
  three are filled in by _fstat().