Add a lowlevel module to pretty print in UTF-8 and color
A module for pretty printing and color should be added. The right place, imho is in cduce-types, that is in : types/misc/.
Once this module is available it could be used for :
- pretty-printing of types (with nice type connectives)
- pretty-printing of error messages or warning in color
- pretty-printing of error messages in tools (configure, dtd2cduce, …)