Update XML library to get rid of last bits of Tango code

[torhus]

ddn-data-xml is an option. But it has to be manually downloaded and installed at the moment, the dub installation fails. And it uses Windows API symbols only available on Vista and later.

And the 32-bit build doesn't work at the moment: https://codeberg.org/ddn/ddn/issues/57

[torhus]

ddn-data-xml's XmlReader is about seven times slower than Tango's SaxParser.