[js] Use $obj.$$iterator instead of nqp.op.iterator($obj) everywhere.

Author: pmurias

src/vm/js/Operations.nqp

@@ -1169,7 +1169,7 @@ class QAST::OperationsJS {
 
             ChunkCPS.new($T_OBJ, $result, [
                 $list,
-                "$iterator = nqp.op.iterator({$list.expr});\n",
+                "$iterator = {$list.expr}.\$\$iterator();\n",
                 "var $loop = function() \{\n",
                 "if ($iterator.idx < $iterator.target) \{\n",
                 $*BLOCK.set_cont($body, $loop),
@@ -1184,7 +1184,7 @@ class QAST::OperationsJS {
         else {
             Chunk.new($T_OBJ, 'null', [
                 $list,
-                "$iterator = nqp.op.iterator({$list.expr});\n",
+                "$iterator = {$list.expr}.\$\$iterator();\n",
                 "while ($iterator.idx < $iterator.target) \{\n",
                 $comp.handle_control($loop, $body),
                 "\}\n"

src/vm/js/nqp-runtime/core.js

@@ -85,11 +85,6 @@ op.setdebugtypename = function(type, debugName) {
   return type;
 };
 
-op.iterator = function(obj) {
-  return obj.$$iterator();
-};
-
-
 exports.hash = function() {
   return new Hash();
 };