CLJS-1476: Self-host: Protocol prefixing broken for three- (or more) segment namespaces

Fixes protocol-prefix fn (two copies, one in core and one
in compiler) for use in self-host. At its core, this function
need to take a string like

  alpha.beta.gamma/IFoo

and turn it into

  alpha$beta$gamma$IFoo$

and it was failing to replace the multiple dot characters
when in self-host mode owing to the fact that .replace
in JavaScript is not a global replace. This fix adds the
"g" flag.

Author: mfikes

src/main/clojure/cljs/compiler.cljc

@@ -906,7 +906,10 @@
     (when (= :expr context) (emits "})()"))))
 
 (defn protocol-prefix [psym]
-  (symbol (str (-> (str psym) (.replace \. \$) (.replace \/ \$)) "$")))
+  (symbol (str (-> (str psym)
+                 (.replace #?(:clj \. :cljs (js/RegExp. "\\." "g")) \$)
+                 (.replace \/ \$))
+            "$")))
 
 (defmethod emit* :invoke
   [{:keys [f args env] :as expr}]

src/main/clojure/cljs/core.cljc

@@ -1190,7 +1190,10 @@
 ;;; end of reducers macros
 
 (core/defn- protocol-prefix [psym]
-  (core/str (core/-> (core/str psym) (.replace \. \$) (.replace \/ \$)) "$"))
+  (core/str (core/-> (core/str psym)
+              (.replace #?(:clj \. :cljs (js/RegExp. "\\." "g")) \$)
+              (.replace \/ \$))
+    "$"))
 
 (def #^:private base-type
      {nil "null"