Supporting the float theory of the SMT-LIB

[Halbaroth]

The current implementation of Alt-Ergo doesn't support the float theory https://smtlib.cs.uiowa.edu/theories-FloatingPoint.shtml but a theory about round functions from the real to subset of real corresponding to finite floats with fixed precision. In particular, our implementation doesn't support infinity values or NaN values.

[bclement-ocp]

Postponing after discussion with the Why3 team, not a priority for now.