Billion laughs is a well-know attack against the internal entity expansion of
XML parsers (https://en.wikipedia.org/wiki/Billion_laughs_attack). The file
"billionlaughs.xxx" is placed here only as an example. The filename extension
must not be changed to ".xml", because the XML validation of IDEs like Eclipse
will also be attacked by this demonstration file as well as editors like
Notepad++!
