* HTML_widget: New. Uniform interface components.
* HTML_reactive.async_div: weaken the type of produced elements.
* CSS: Make button, button. (Still an ugly one.)
* CORE_client_action: New. Client-side control operators of server-side processes.
* HTML_autotest: Play with it.
* HTML_widget: A button is a span, not a div!
CORE_client_action: Fix a mispelling.
* CORE_client_action: Cosmetics.
* COMMON_pervasives: New. Complement OCaml standard library when needed.