Removed ownership of some windows from the CommonPool. Removed unuseful 'Enable Undo' menu, the undo should be active always. Removed RedrawWindow from CommonPool, added the needed methods to WindowsManager and reworked all the code to use it. Added to WindowsManager a IsWindowValid() method useful if you want to check it a window is already opened or it was deleted. Within those changes the program's functionalities are mantained working.Added new classes taken from the Haiku's media_kitm to the internal audio API codebase.