p labeled with label "model_projected" for that it exists a projection
function f creates declaration of new constant c and axiom stating that
c = f p

Projection functions are functions tagged with meta "model_projection".
Function f is projection function for abstract function and predicate p
if f is tagged with meta "model_projection" and has a single argument
of the same type as is the type of p.

This transformation is needed in situations when we want to display not
value of a variable, but value of a projection function applied to a variable.

Note that since Why3 supports namespaces (different projection functions
can have the same name) and input languages of solvers typically not,
Why3 renames projection functions to avoid name clashes.
This is why it is not possible to just store the name of the projection
function in a label and than query the solver directly for the value of
the projection.
Also, it means that this transformation should thus be executed before
this renaming.