V3 PATCH: Fix const-correctness in use of iconv

[law@redhat.com]

  In message < flu29h3wyj.fsf@sel.cmla.ens-cachan.fr >you write:
  > OK.  It has been practice in V3 to document the intent of ChangeLog
  > entries (especially for tricky issues) even if the code is documented,
  > it makes it easier to follow changes history.  Well, now V3 is
  > operating under GNU policies and I missed that :-)
Note that we sometimes put a quick blurb in large complex ChangeLog entries
for the intent of the change, followed by the standard ChangeLog verbage.

jeff