QbsProjectManager: Put internal classes into the Internal namespace.

Change-Id: I5fa1ce2ed709b7904a0b2701133794751e5e2119
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>

src/plugins/qbsprojectmanager/defaultpropertyprovider.cpp

@@ -50,6 +50,8 @@
 
 namespace QbsProjectManager {
 using namespace Constants;
+
+namespace Internal {
 using namespace ProjectExplorer::Constants;
 using namespace Ios::Constants;
 using namespace Qnx::Constants;
@@ -237,4 +239,5 @@ QVariantMap DefaultPropertyProvider::autoGeneratedProperties(const ProjectExplor
     return data;
 }
 
+} // namespace Internal
 } // namespace QbsProjectManager