* sql/*.lisp: Add db-type parameter to generic functions READ-SQL-VALUE,
DATABASE-GET-TYPE-SPECIFIER, and OUTPUT-SQL-VALUE-AS-TYPE. Update methods to use these.
* sql/generic-postgresql.lisp, sql/generic-odbc.lisp: New files
* sql/*.lisp: Add db-type parameter to generic functions READ-SQL-VALUE,
DATABASE-GET-TYPE-SPECIFIER, and OUTPUT-SQL-VALUE-AS-TYPE. Update methods to use these.
* sql/generic-postgresql.lisp, sql/generic-odbc.lisp: New files