mu4e: updates for core changes

Deal with (name . email) --> (:name "boo" :email "boo@example.com")
Add support for the new "changed" field.

mu4e/mu4e-compose.el

@@ -859,8 +859,8 @@ buffer buried."
   (when other-headers
     (dolist (h other-headers other-headers)
       (if (symbolp (car h)) (setcar h (symbol-name (car h))))
-      (message-add-header (concat (capitalize (car h)) ": " (cdr h) "\n"  ))
-      ))
+      (message-add-header
+       (concat (capitalize (car h)) ": " (cdr h) "\n"  ))))
 
   ;; yank message
   (if (bufferp yank-action)