Add QT_BEGIN_HEADER/QT_END_HEADER macros

Fixing `macros' function test of `tst_headers'

Task-number: QTQAINFRA-324

Change-Id: I9e78d5f33dcd89718d90e0d2a40a02eba80f6ca9
Reviewed-by: Liang Qi <liang.qi@nokia.com>

src/widgets/kernel/qplatformdialoghelper_qpa.h

@@ -45,6 +45,8 @@
 #include <qglobal.h>
 #include <qdialog.h>
 
+QT_BEGIN_HEADER
+
 QT_BEGIN_NAMESPACE
 
 class QString;
@@ -79,4 +81,6 @@ public:
 
 QT_END_NAMESPACE
 
+QT_END_HEADER
+
 #endif // QPLATFORMDIALOGHELPER_H