CMake: Fix lightmaps example to build in a namespaced Qt

Add misisng namespace bits.

The example is built by a CMake configuration.
It is not built in a qmake configuration due to a missing
x11 / embedded requirement.

Task-number: QTBUG-84881
Change-Id: I6c53299a53e7c4e19d994ec2ae2d542667d41899
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

examples/embedded/lightmaps/slippymap.cpp

@@ -53,10 +53,18 @@
 #include "slippymap.h"
 #include "qmath.h"
 
+#ifdef QT_NAMESPACE
+QT_BEGIN_NAMESPACE
+size_t qHash(const QT_NAMESPACE::QPoint& p)
+#else
 size_t qHash(const QPoint& p)
+#endif
 {
     return p.x() * 17 ^ p.y();
 }
+#ifdef QT_NAMESPACE
+QT_END_NAMESPACE
+#endif
 
 // tile size in pixels
 const int tdim = 256;

examples/embedded/lightmaps/slippymap.h

@@ -55,8 +55,10 @@
 #include <QPixmap>
 #include <QUrl>
 
+QT_BEGIN_NAMESPACE
 class QNetworkReply;
 class QPainter;
+QT_END_NAMESPACE
 
 class SlippyMap: public QObject
 {
@@ -94,3 +96,4 @@ private:
 };
 
 #endif
+