Fix OSX button order issue in Unsaved Changes dialog.

Also changes the presentation of the string when the checkbox appears
so that the "Changes will be lost" warning isn't hidden by the turndown.
This last part may require conditional compilation as it's undocumented.

Lastly, regularizes the Unsaved Changes strings between the apps.

pcbnew/initpcb.cpp

@@ -104,8 +104,8 @@ bool FOOTPRINT_EDIT_FRAME::Clear_Pcb( bool aQuery )
     {
         wxSafeYield( this, true );      // Allow frame to come to front before showing warning.
 
-        if( !HandleUnsavedChanges( this,
-                    _( "The current footprint has been modified.  Save changes?" ),
+        if( !HandleUnsavedChanges( this, _( "The current footprint has been modified.  "
+                                            "Save changes?" ),
                     [&]() -> bool { return SaveFootprint( GetBoard()->Modules().front() ); } ) )
         {
             return false;