Fix `Svg.animate` type, name and attributes

[rand00]

[rand00]

I needed to change the type of Xml to include a Semicolon separator - which demands change to js_of_ocaml-tyxml too. I'll push a PR there too

[rand00]

This PR includes #306

[Drup]

The change to the signature of Xml.S is a rather big breaking change (it breaks not only js_of_ocaml, but also eliom, and all users of the functorial API).

I feel in this case, maybe it's for the best to first do all the renaming and deprecations, make a small release with all the other accumulated small fixes, then make a new big release (with some other breaking changes I accumulated).

[rand00]

Okay - but one can't use the Svg.animate with animation-values and key-times without this major change; so makes Svg.animate quite useless anyway. Could postpone the renaming because of that?

[Drup]

Well, you can always implement it in term of string_attrib. It has less good properties, but it should be sufficient in practice for now.