Create optimized versions of the Map/Set clear method

src/collection.js

Index: src/collection.js
diff --git a/src/collection.js b/src/collection.js
index 3f6d105447962ff65705fb02e18144336774b579..94bda703578ea73829efda3a7db96705f614d54b 100644
--- a/src/collection.js
+++ b/src/collection.js
@@ -92,7 +92,7 @@ function SetClearJS() {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Set.prototype.clear', this]);
   }
-  %SetClear(this);
+  %_SetClear(this);
 }
 
 
@@ -245,7 +245,7 @@ function MapClearJS() {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Map.prototype.clear', this]);
   }
-  %MapClear(this);
+  %_MapClear(this);
 }