floatformat.c (floatformat_i387_ext_is_valid): Use explicit cast to convert from "from".

        * floatformat.c (floatformat_i387_ext_is_valid): Use explicit cast
        to convert from "from".
        (floatformat_to_double): Likewise.
        (floatformat_from_double): Use explicit cast to convert from "to".

From-SVN: r108717