DirManager.cpp doesn't depend on Clipboard...

... Locate other outstanding DirManagers by other means, a global tracking
array.

This does not yet break any dependency cycles.

src/Benchmark.cpp

@@ -359,7 +359,7 @@ void BenchmarkDialog::OnRun( wxCommandEvent & WXUNUSED(event))
    HoldPrint(true);
 
    ZoomInfo zoomInfo(0.0, ZoomInfo::GetDefaultZoom());
-   auto dd = std::make_shared<DirManager>();
+   auto dd = DirManager::Create();
    const auto t = TrackFactory{ dd, &zoomInfo }.NewWaveTrack(int16Sample);
 
    t->SetRate(1);