[OSX] prevent osx from inserting View and Help menu options.

native/Avalonia.Native/src/OSX/app.mm

@@ -15,6 +15,10 @@ NSApplicationActivationPolicy AvnDesiredActivationPolicy = NSApplicationActivati
         }
         
         [[NSApplication sharedApplication] setActivationPolicy: AvnDesiredActivationPolicy];
+        
+        [[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"NSFullScreenMenuItemEverywhere"];
+        
+        [[NSApplication sharedApplication] setHelpMenu: [[NSMenu new] initWithTitle:@""]];
     }
 }
 

native/Avalonia.Native/src/OSX/window.mm

@@ -425,6 +425,7 @@ private:
         WindowEvents = events;
         [Window setCanBecomeKeyAndMain];
         [Window disableCursorRects];
+        [Window setTabbingMode:NSWindowTabbingModeDisallowed];
     }
     
     virtual HRESULT Show () override