Make the SVG sigs wrappable in a monad.
Make the html wrappable in a monad.
Modify the way the wraping monad is used so that it compiles.

The wraping monad is now in a separated module. The Xml module contains
only the type 'a wrap. Functors in Html_f and Svg_f are specialized
accordingly. Each functor have a version partialy applied again the
empty monad.
Add more type informations so that the wraping is transparent for the M module.
Regenerate dependencies.
missing cmi
Update to new master.