( Note that the last word is always skipped because it's not
possible to reliably detect its end. If you need that last
word, define a dummy word before calling RLDICT.

We first start by copying the affected area to H@+4. This is
where the relinking will take place.

Then we iterate the new dict from the top, keeping track of
wr, the current wordref and we, wr's end offset.

Initially, we get our wr and we, withH@ and CURRENT, which we
offset by u+4. +4 before, remember, we're using 4 bytes
as variable space.

At each iteration, we becomes wr-header and wr is fetched from
PREV field. )