Bug 337 - New logger class allows log to be initialized immediately without crashing Mac empty project windows

This is an older one...originally from 2011.  Bug says it all, but basically it allows logging
to begin immediately upon startup for all platforms.  And it has multithreading protection, so
it should now be safe to log from the non-GUI threads.

src/AudacityApp.h

@@ -33,6 +33,7 @@ class IPCServ;
 class Importer;
 class CommandHandler;
 class AppCommandEvent;
+class AudacityLogger;
 
 void SaveWindowSize();
 
@@ -187,9 +188,9 @@ class AudacityApp:public wxApp {
    bool GetWindowRectAlreadySaved()const {return mWindowRectAlreadySaved;}
    void SetWindowRectAlreadySaved(bool alreadySaved) {mWindowRectAlreadySaved = alreadySaved;}
 
-   Importer *mImporter;
+   AudacityLogger *GetLogger();
 
-   wxLogWindow *mLogger;
+   Importer *mImporter;
 
 #if defined(__WXGTK__)
    /** \brief This flag is set true when in a keyboard event handler.