Utils::Json: Clean include directives.

Change-Id: I6be3acaafcdb68aa9220d97ae79bcac8508dd294
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

src/libs/utils/json.cpp

@@ -40,6 +40,8 @@
 #include <QFile>
 #include <QStringBuilder>
 #include <QDebug>
+#include <QVariant>
+#include <QScriptEngine>
 
 using namespace Utils;