Dolmen_stdSourceStandard imlplementation of statements. This module provides a reasonable and standard implementation of statements, that can directly be used to instantiated the various functors of the dolmen library. These statements are closer to smtlib statements than to other languages statements because it is easier to express other languages statements using smtlib's than the other way around. Still, a generalisation of smtlib statements was needed so as not to lose some important distinctions between conjectures and assertions for instance.