• Resurrect and apply unofficial patch from Gentoo to build against Qt version 5 (this breaks unetbootin::lstFtpDirFiles() due to https://bugreports.qt.io/browse/QTBUG-26294)
• Comment out all sources that require FTP LIST command
• Don't wait until file is fully downloaded before dumping it on disk
• Fix some QNetworkReply/QFile resource freeing bugs
• Delete unetbootin::dlprogressupdate64() because it's never used
• Fix some slot warnings while here

Patches by: Valeriy Malov <jazzvoid@gmail.com>
Obtained from: https://bugs.gentoo.org/show_bug.cgi?id=644360