Steve's patch for http://bugzilla.audacityteam.org/show_bug.cgi?id=687

Changes in AudacityProject::SaveAs() warning dialogs, per 'Save Project warning' discussion on audacity-quality, plus some further changes of my own.

Similar changes for 'Save Compressed Project'.

Added Cancel button to both warnings, so user can opt out immediately, rather than have to wait another dialog. 


Added wxMessageBox's best 'warning' icon to our WarningDialog constructor, so it shows in title bar. It's low-rez (32x32), but all that's available with wxWidgets 2.8.12. Easy to remove if too ugly.

src/widgets/Warning.cpp

@@ -23,6 +23,7 @@ the ability to not see similar warnings again for this session.
 #include "../Prefs.h"
 #include "../ShuttleGui.h"
 
+#include <wx/artprov.h>
 #include <wx/button.h>
 #include <wx/checkbox.h>
 #include <wx/dialog.h>
@@ -55,6 +56,7 @@ WarningDialog::WarningDialog(wxWindow *parent, wxString message, bool showCancel
             wxDefaultPosition, wxDefaultSize, 
             (showCancelButton ? wxDEFAULT_DIALOG_STYLE : wxCAPTION | wxSYSTEM_MENU)) // Unlike wxDEFAULT_DIALOG_STYLE, no wxCLOSE_BOX.
 {
+   SetIcon(wxArtProvider::GetIcon(wxART_WARNING, wxART_MESSAGE_BOX));
    ShuttleGui S(this, eIsCreating);
 
    S.SetBorder(10);