Documentation: Add examples for Q_NAMESPACE(_EXPORT)

It is not obvious how to use them.

Change-Id: I60fdfb95f4c29cbc310d149495ebb38964e5a9ac
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

src/corelib/kernel/qobject.cpp

@@ -4614,6 +4614,14 @@ QDebug operator<<(QDebug dbg, const QObject *o)
     \c{staticMetaObject} is of type QMetaObject and provides access to the
     enums declared with Q_ENUM_NS/Q_FLAG_NS.
 
+    For example:
+
+    \code
+    namespace test {
+    Q_NAMESPACE
+    ...
+    \endcode
+
     \sa Q_NAMESPACE_EXPORT
 */
 
@@ -4630,6 +4638,14 @@ QDebug operator<<(QDebug dbg, const QObject *o)
     is declared with the supplied \a EXPORT_MACRO qualifier. This is
     useful if the object needs to be exported from a dynamic library.
 
+    For example:
+
+    \code
+    namespace test {
+    Q_NAMESPACE_EXPORT(EXPORT_MACRO)
+    ...
+    \endcode
+
     \sa Q_NAMESPACE, {Creating Shared Libraries}
 */