uiop/utility: use find-symbol* for find-standard-case-symbol

NAME-DESIGNATOR and PACKAGE-DESIGNATOR will be converted to a string using STRING-DESIGNATOR on an

ANSI CL platform, or STRING on a so-called \"modern\" platform such as Allegro with modern syntax.

If optional ERROR argument is NIL, return NIL instead of an error when the symbol is not found."

    (find-symbol (standard-case-symbol-name name-designator)

    (find-symbol* (standard-case-symbol-name name-designator)

                  (etypecase package-designator

                    ((or package null) package-designator)

                    ((or string symbol)))