- Add a new type of restriction: -hC, which restricts to closures
  whose CCS contains the specified CCs *anywhere* (not just at the
  top).

- Complain if the user tries to request both retainer and biographical
  profiling.  We don't support both simultaneously, because they use
  the same header word in the closure.

- Allow for the fact that the heap might contain some closures which
  don't have a valid retainer set during the heap census.  The only
  known closures of this kind so far are DEAD_WEAK closures.

- Some cruft-removal and renaming of functions to follow conventions.