Also print the class name in the QObject::killTimer error msg.

When no objectName is set, this will give at least some information,
other than the memory address of the current instance.

Change-Id: Iae452c0e9fe38f0aab35094ddf0edc0fd6b28c20
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

src/corelib/kernel/qobject.cpp

@@ -1636,9 +1636,10 @@ void QObject::killTimer(int id)
         int at = d->extraData ? d->extraData->runningTimers.indexOf(id) : -1;
         if (at == -1) {
             // timer isn't owned by this object
-            qWarning("QObject::killTimer(): Error: timer id %d is not valid for object %p (%s), timer has not been killed",
+            qWarning("QObject::killTimer(): Error: timer id %d is not valid for object %p (%s, %s), timer has not been killed",
                      id,
                      this,
+                     metaObject()->className(),
                      qPrintable(objectName()));
             return;
         }