Update system.cpp

Cleaned up to use the preferred namespace code.  This can be further simplified by using the HString/HStringReference classes from wrl\wrappers\corewrappers.h

modules/core/src/system.cpp

@@ -107,7 +107,7 @@ std::wstring GetTempPathWinRT()
     if (FAILED(WindowsCreateStringReference(RuntimeClass_Windows_Storage_ApplicationData,
                                             (UINT32)wcslen(RuntimeClass_Windows_Storage_ApplicationData), &hstrHead, &str)))
         return wstr;
-    if (FAILED(RoGetActivationFactory(str, IID_PPV_ARGS(appdataFactory.ReleaseAndGetAddressOf()))))
+    if (FAILED(Windows::Foundation::GetActivationFactory(str, appdataFactory.ReleaseAndGetAddressOf())))
         return wstr;
     if (FAILED(appdataFactory->get_Current(appdataRef.ReleaseAndGetAddressOf())))
         return wstr;