GLUT: Fix message handling in GlutWindow

Call the superclass implementation of MessageReceived() to process messages not
handled by GlutWindow itself.

This restores mouse and keyboard functionality in OpenGL apps, including
Celestia, affected by commit 75e5739772.

Change-Id: Ic3af56ab2f78e8b2b8be576d2edc30bb7357f359
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1862
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

src/libs/glut/glutEvent.cpp

@@ -801,6 +801,7 @@ void GlutWindow::MessageReceived(BMessage *message)
 	 	break;
 	}
 	default:
+		BGLView::MessageReceived(message);
 	 	break;
 	}
 }