Include QObject for the required definitions

--- src/plugins/TabManager/tldextractor/tldextractor.h	2015-01-26 15:26:15.000000000 +0100
+++ src/plugins/TabManager/tldextractor/tldextractor.h	2015-07-06 18:41:27.630175234 +0200
@@ -20,6 +20,7 @@
 
 #define TLDExtractor_Version "1.0"
 
 #include <QHash>
+#include <QObject>
 #include <QStringList>
 
