Fix broken FileZilla package: change URL

Your FileZilla package is not updating anymore, because the installer (starting from 3.9.0) is now only downloadable via SourceForge. As you probably know, SourceForge is a bit tricky to use with Ketarin, because Ketarin lacks of following HTTP 301/302 redirects which are used there.

I had to “misuse” the `{{DownloadUrlx64}}` substitution variable as 32-bit download URL, otherwise the package would contain a specific mirror URL, which is bad (not all mirrors aren’t always online and some are slow sometimes).

No worries about the adware that was bundled with the FileZilla installer on Windows some time ago. The installer is now adware-free.
Yes that’s really weird. Not for all projects hosted on SourceForge this is the possible way.

Some projects only work with the HTTP 301/302 redirect method and some use a `<meta http-equiv="refresh" content="5; …` tag in a HTML response.

I also had this problem with some of my packages, but I found a solution. Here’s a gist of the working Ketarin job for stexbar where I applied the fixes: https://gist.github.com/TomOne/9aaac42ece27e0480e69

The solution is to:

1. Set an user agent in the Ketarin job that corresponds to one of a common browser, I used the one from Chrome.
2. Now the Ketarin variable which uses the URL http://sourceforge.net/projects/stefanstools/files/StExBar/StExBar-1.8.6.msi/download as source contains a HTML response where you pick the name mirror that comes after the string `use_mirror=`. Then you can construct `{preupdate-url}` with the mirror name.

Conclusion: I don’t like SourceForge. I recommend to every developer to use GitHub instead. GH is better in all things and doesn’t make it so hard to download files. I hope that SF dies, just like Google Code should. :angry: