Get rid of nested functions declarations that are not on top level (causes strict mode warnings)

lib/io.js

 /*
  * This file is part of the Adblock Plus,
  * Copyright (C) 2006-2012 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 171 matching lines @@
             let e = Cc["@mozilla.org/js/xpc/Exception;1"].createInstance(Ci.nsIXPCException);
             e.initialize("File write operation failed", result, null, Components.stack, file, null);
             callback(e);
           }
           else
             callback(null);
         }
       }, null);
 
       let lineBreak = this.lineBreak;
-      function writeNextChunk()
+      let writeNextChunk = function()
       {
         let buf = [];
         let bufLen = 0;
         while (bufLen < 0x4000)
         {
           try
           {
             let str = data.next();
             buf.push(str);
             bufLen += str.length;
@@ skipping 34 matching lines @@
             }
             else
               outStream.close();
 
             if (timeLineID)
             {
               TimeLine.asyncEnd(timeLineID);
             }
           }
         }, 0, 0, Services.tm.currentThread);
-      }
+      };
       writeNextChunk();
     }
     catch (e)
     {
       callback(e);
     }
   },
 
   /**
    * Copies a file asynchronously. The callback will be called when the copy
@@ skipping 72 matching lines @@
         isFile: exists && file.isFile(),
         lastModified: exists ? file.lastModifiedTime : 0
       });
     }
     catch(e)
     {
       callback(e);
     }
   }
 }