Replace most inclusions of MemoryX.h with <memory> ...

... Most often it was needed for a custom definition of std::make_unique, but
we build C++14 now.

src/ModuleManager.cpp

@@ -30,6 +30,7 @@ i.e. an alternative to the usual interface, for Audacity.
 #include <wx/filename.h>
 
 #include "FileNames.h"
+#include "MemoryX.h"
 #include "PluginManager.h"
 
 #include "audacity/PluginInterface.h"