input-rest broken when input is "base-string"

[jasom]

This is an issue on ECL which makes strings base-string unless they contain non base-chars; for example (type-of "") => (SIMPLE-ARRAY BASE-CHAR (0))

The fix is fairly easy; you can either specialize input-rest for base-string, or add this to the beginning of input-rest for cl:string:

(when (not (equal (array-element-type input)
              (upgraded-array-element-type 'character)))
      (setf input
        (make-array (length input) :element-type 'character
            :initial-contents input)))

[jasom]

Created a pull request for this one, so closing