Dictd: Support extended Dictd format (--index-keep-orig) with 4 entries in the index

See the dictfmt man:

 --index-keep-orig
    When --utf-8 is specified  headwords  are  lowercased  and  non-
    alphanumeric  characters  are  removed  from it before saving to
    .index  file  in   order   to   simplify   the   search.    When
    --index-keep-orig  option  is  used fourth column is created (if
    necessary) in .index file, and  contains  an  original  headword
    which  is  returned by MATCH command.  This option may be useful
    to prevent converting " AT&T" to " ATT" or to keep proper  nouns
    with uppercased first letter.