QGestureManager: fix UB (invalid pointer comparison)

Comparing pointers with op< that do not point into the same array is
UB. Fix, in the usual way, by using std::less.

Change-Id: Id2c957557719887b2016632d683dbab8af07b34c
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/widgets/kernel/qgesturemanager_p.h

@@ -59,6 +59,8 @@
 
 #ifndef QT_NO_GESTURES
 
+#include <functional>
+
 QT_BEGIN_NAMESPACE
 
 class QBasicTimer;
@@ -112,7 +114,7 @@ private:
         ObjectGesture(QObject *o, const Qt::GestureType &g) : object(o), gesture(g) { }
         inline bool operator<(const ObjectGesture &rhs) const
         {
-            if (object < rhs.object)
+            if (std::less<QObject *>{}(object, rhs.object))
                 return true;
             if (object == rhs.object)
                 return gesture < rhs.gesture;