... Unnecessary because transitively included.
But each .cpp file still includes its own .h file near the top to ensure
that it compiles indenendently, even if it is reincluded transitively later.
... Should have no effect on generated code, except perhaps some slight faster
virtual function calls. Mostly useful as documentation of design intent.
Tried to mark every one of our classes that inherits from another, or is a
base for others, or has abstract virtual functions, and a few others besides.
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.
