* src/xwidget.c (Fxwidget_delete_zombies): Re-implemented in Lisp.
Note: It is not longer necessary to delete xwidget with killed buffer
here because it is done automatically when a buffer is killed.
(Fdelete_xwidget_view): New function to delete the given
xwidget-view.
* lisp/xwidget.el (xwidget-delete-zombies): Re-implementation.
* src/xwidget.c (Fxwidget_info): Fix a regression introduced in commit
b4e1725be1b96b5335a12d34fdd81b99dededf54.
* src/xwidget.h (xwidget): Remove old todo.
* src/xwidget.c (xwidget_init_view): Prevent an error while displaying a
xwidget of type `cairo' but doesn't do anything useful.