Support extend-type function IPrintWithWriter

Let's users do

(extend-type function
  IPrintWithWriter
  (-pr-writer [obj writer _]
    (let [name (.-name obj)
          name (if (empty? name)
                 "Function"
                 name)]
      (write-all writer "#object[" name "]"))))

src/main/cljs/cljs/core.cljs

@@ -9068,11 +9068,13 @@ reduces them without incurring seq initialization"
           (-write writer obj))
 
         ^boolean (goog/isFunction obj)
-        (let [name (.-name obj)
-              name (if (or (nil? name) (gstring/isEmpty name))
-                     "Function"
-                     name)]
-          (write-all writer "#object[" name " \"" (str obj) "\"]"))
+        (if (satisfies? IPrintWithWriter obj)
+          (-pr-writer obj writer opts)
+          (let [name (.-name obj)
+                name (if (or (nil? name) (gstring/isEmpty name))
+                       "Function"
+                       name)]
+            (write-all writer "#object[" name " \"" (str obj) "\"]")))
 
         (instance? js/Date obj)
         (let [normalize (fn [n len]