Fix remaining Qt6 build errors after PR #540

- qetxml.h: add missing <QUuid> include (used in propertyUuid/
  createXmlProperty signatures but never included directly).
- machine_info.cpp: fix ambiguous QString/int operator> in
  send_info_to_debug() for it1/it2/it3; just count every
  matching file found instead of the meaningless comparison.

sources/qetxml.h

@@ -20,6 +20,7 @@
 
 #include <QDomElement>
 #include <QPen>
+#include <QUuid>
 
 class QDomDocument;
 class QDir;