compat: Add 'string-for-each' for Mes.

* gash/compat.scm [mes] (string-for-each): New procedure.

gash/compat.scm

@@ -86,6 +86,7 @@
           make-parameter
           parameterize
           set-port-line!
+          string-for-each
           string-concatenate-reverse
           string-every
           string-any
@@ -143,6 +144,9 @@
      ((procedure? pred) pred)
      (else (error "Invalid character predicate."))))
 
+  (define (string-for-each proc str)
+    (for-each proc (string->list str)))
+
   (define (string-every pred str)
     ((@ (srfi srfi-1) every) (char-pred pred) (string->list str)))