Automatic update

tuned error msgs;

improved type check error messages;

renamed set_ap to setmp;

Automatic updates

Removed the \date{} command in order to put the date of typesetting on the title page

Corrected the informal description of coinductive definition

Corrected the informal description of coinductive definition in sections 1 and 4.3, introducing the notion of "consistent with" a set of rules. Final version for Milner Festschrift?

Added ability to have case expressions involving tuples. (via translation)

tuned;