clean up how we set *print-fn* *print-err-fn* so it's easier to debug

Author: swannodette

src/main/cljs/cljs/core.cljs

@@ -186,10 +186,10 @@
   "Set *print-fn* to console.log"
   []
   (set! *print-newline* false)
-  (set! *print-fn*
+  (set-print-fn!
     (fn [& args]
       (.apply (.-log js/console) js/console (into-array args))))
-  (set! *print-err-fn*
+  (set-print-err-fn!
     (fn [& args]
       (.apply (.-error js/console) js/console (into-array args))))
   nil)
@@ -11498,10 +11498,10 @@ reduces them without incurring seq initialization"
     (identical? *target* "nashorn")
     (let [system (.type js/Java "java.lang.System")]
       (set! *print-newline* false)
-      (set! *print-fn*
+      (set-print-fn!
         (fn [& args]
           (.println (.-out system) (.join (into-array args) ""))))
-      (set! *print-err-fn*
+      (set-print-err-fn!
         (fn [& args]
           (.println (.-error system) (.join (into-array args) "")))))))
 

src/main/cljs/cljs/nodejs.cljs

@@ -18,10 +18,10 @@
 
 (defn enable-util-print! []
   (set! *print-newline* false)
-  (set! *print-fn*
+  (set-print-fn!
     (fn [& args]
       (.apply (.-log js/console) js/console (into-array args))))
-  (set! *print-err-fn*
+  (set-print-err-fn!
     (fn [& args]
       (.apply (.-error js/console) js/console (into-array args))))
   nil)

src/main/cljs/clojure/browser/repl.cljs

@@ -43,9 +43,9 @@
   (when-let [conn @xpc-connection]
     (flush-print-queue! conn)))
 
-(set! *print-fn* repl-print)
-(set! *print-err-fn* repl-print)
 (set! *print-newline* true)
+(set-print-fn! repl-print)
+(set-print-err-fn! repl-print)
 
 (defn get-ua-product []
   (cond