`eword-decode-field'.
* lisp/nnheader.el (make-full-mail-header): Use `eword-decode-field'.
       (let ((funcs message-make-forward-subject-function)
            (subject (if message-wash-forwarded-subjects
                         (message-wash-subject
-                         (or (eword-decode-unstructured-field-body
-                              (message-fetch-field "Subject")) ""))
-                      (or (eword-decode-unstructured-field-body
-                           (message-fetch-field "Subject")) ""))))
+                         (or (eword-decode-field
+                               'Subject (message-fetch-field "Subject"))
+                               ""))
+                      (or (eword-decode-field
+                            'Subject (message-fetch-field "Subject"))
+                           ""))))
        ;; Make sure funcs is a list.
        (and funcs
             (not (listp funcs))