[js] Add 'use strict'

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

@@ -1,3 +1,4 @@
+'use strict';
 var NQPException = require('./nqp-exception.js');
 
 function NQPArray(array) {

src/vm/js/nqp-runtime/code-ref.js

@@ -1,3 +1,4 @@
+'use strict';
 CodeRef.cuids = {};
 function CodeRef(name, cuid) {
   this.name = name;

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

@@ -1,4 +1,4 @@
-"use strict";
+'use strict';
 var sixmodel = require('./sixmodel.js');
 var Hash = require('./hash.js');
 var NQPInt = require('./nqp-int.js');

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

@@ -1,3 +1,4 @@
+'use strict';
 function STable(REPR, HOW) {
   this.REPR = REPR;
   this.HOW = HOW;