Note [CAF lists]

  dyn_caf_list  (CAFs chained through static_link)
     This is a chain of all CAFs in the program, used for
     dynamically-linked GHCi.
     See Note [dyn_caf_list].

  debug_caf_list  (CAFs chained through saved_info)
     A chain of all *live* CAFs in the program, that does not keep
     the CAFs alive.  Used for detecting when we enter a GC'd CAF,
     and to give diagnostics with +RTS -DG.

  revertible_caf_list  (CAFs chained through static_link)
     A chain of CAFs in object code loaded with the RTS linker.
     These CAFs can be reverted to their unevaluated state using
     revertCAFs.

Pointers in these lists are tagged with STATIC_FLAG_LIST, so when
traversing the list remember to untag each pointer with
UNTAG_STATIC_LIST_PTR().