pattern: Adjust for Mes.

* gash/pattern.scm (substring->list): New procedure.
(character-range): Use it.

gash/pattern.scm

@@ -21,6 +21,7 @@
   #:use-module (ice-9 receive)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-9 gnu)
+  #:use-module (srfi srfi-14)
   #:use-module (srfi srfi-26)
   #:use-module (gash compat srfi-43)
   #:export (parse-pattern
@@ -31,6 +32,16 @@
             pattern-drop
             pattern-drop-right))
 
+(cond-expand
+ (mes
+  ;; Mes does not allow a range for 'string->list'.  We use this so
+  ;; infrequently, that we just define a new procedure for when we
+  ;; need it.
+  (define (substring->list string start end)
+    (string->list (substring string start end))))
+ (else
+  (define substring->list string->list)))
+
 (define-immutable-record-type <pattern>
   (make-pattern parts)
   pattern?
@@ -77,7 +88,7 @@
               (match (string-index str end)
                 (#f (loop tail))
                 (eindex (if (<= sindex eindex)
-                            (string->list str sindex (1+ eindex))
+                            (substring->list str sindex (1+ eindex))
                             (loop tail))))))))))))
 
 (define* (parse-matching-bracket-expression s #:optional (start 0)