close button reimplementation

Somehow I have to provide the toolbarButton-close.png, but I dont know how it works via github, so if I can just send someone the file I would be happy...

Edit: just found the "choose an image" link and put the close cross here -->![toolbarButton-close](https://f.cloud.github.com/assets/3731697/317582/2a89bc94-9879-11e2-9543-2f128a230712.png)<--
It has to go in "3rdparty/pdfjs/images"