Call QWARN() instead of QTest::qWarn().

The QWARN macro wraps QTest::qWarn(), but the former is the public API
and the latter is merely an implementation detail that is subject to
change.

Change-Id: I02ae5ea384875afb7f235ef8dff0768a56afaa53
Reviewed-on: http://codereview.qt-project.org/5486
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>

src/qmltest/quicktestevent.cpp

@@ -162,7 +162,7 @@ namespace QtQuickTest
             static const char *mouseActionNames[] =
                 { "MousePress", "MouseRelease", "MouseClick", "MouseDoubleClick", "MouseMove" };
             QString warning = QString::fromLatin1("Mouse event \"%1\" not accepted by receiving window");
-            QTest::qWarn(warning.arg(QString::fromLatin1(mouseActionNames[static_cast<int>(action)])).toAscii().data());
+            QWARN(warning.arg(QString::fromLatin1(mouseActionNames[static_cast<int>(action)])).toAscii().data());
         }
     }