[Bug fixed]
The --with-db185 option of configure script generated the following error:

        $ ./configure LIBS=-lpthread --with-db185-compat=/usr/local/BerkeleyDB.6.1
        ...
        $ make
        ...
        assoc.c:67:34: error: too few arguments to function call, expected 2, have 1
                (void)assoc->db->close(assoc->db);
                      ~~~~~~~~~~~~~~~~          ^
        1 error generated.

Now, it works.