Issue 5552 - use strict mode for all JS in libadblocklus

lib/compat.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 16 matching lines @@
 }
 require.scopes = {__proto__: null};
 
 function importAll(module, globalObj)
 {
   var exports = require(module);
   for (var key in exports)
     globalObj[key] = exports[key];
 }
 
-onShutdown = {
+const onShutdown = {
   done: false,
   add: function() {},
   remove: function() {}
 };
 
 //
 // XPCOM emulation
 //
 
 const Components =
@@ skipping 386 matching lines @@
         var kValue = o[k];
         if (predicate.call(thisArg, kValue, k, o)) {
           return kValue;
         }
         // e. Increase k by 1.
         k++;
       }
     }
   });
 }