fixes for the mimetype icons

core/img/filetypes/application-pdf.png

core/img/filetypes/application-rss+xml.png

core/img/filetypes/image-svg+xml.png

core/img/filetypes/msword.png

core/img/filetypes/text-calendar.png

core/img/filetypes/text-css.png

core/img/filetypes/text-html.png

core/img/filetypes/text-x-c++.png

core/img/filetypes/text-x-c.png

core/img/filetypes/text-x-csharp.png

core/img/filetypes/text-x-h.png

files/js/filelist.js

lib/helper.php