Separate versions of DoImportMIDI that do and don't assume a project

src/Menus.h

@@ -106,6 +106,9 @@ public:
 
 /// Namespace for functions for File menu
 namespace FileActions {
+// Import into existing project
+bool DoImportMIDI( AudacityProject &project, const FilePath &fileName );
+// Import file, creating a project if the first argument is null
 AudacityProject *DoImportMIDI(
    AudacityProject *pProject, const FilePath &fileName );
 }