Fix Windows build build with namespaced Qt

For real this time. Amends 8dd8d68bdc.

Fixes: QTCREATORBUG-22305
Change-Id: I61133f76b7e39a2b0168f8a6c19721231d443807
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/shared/proparser/registry.cpp

@@ -29,6 +29,8 @@
 #include <QtCore/qstringlist.h>
 #include "registry_p.h"
 
+QT_BEGIN_NAMESPACE
+
 namespace QMakeInternal {
 
 #ifdef Q_OS_WIN32
@@ -156,3 +158,4 @@ QString qt_readRegistryKey(HKEY parentHandle, const QString &rSubkey, unsigned l
 
 }  // namespace QMakeInternal
 
+QT_END_NAMESPACE