r9478: 25 May 2004 Kevin Rosenberg <kevin@rosenberg.net>

        * sql/oodml.lisp: (string n) now produces a CHAR field. Add new VARCHAR
        type. Added *default-varchar-length* rather than previous hard-coded
        varchar length. Remove 'simple-string and 'simple-base-string since they
        are subtypes of 'string.
        * db-oracle/oracle-sql.lisp: Use *default-varchar-length* rather than
        local hard-coded value.
        * sql/metaclasses.lisp: Convert specified type VARCHAR and (VARCHAR n) to Lisp
        type string. Convert specified-type (CHAR n) to string. Convert specified-type
        CHAR to lisp type character.