[ 2 new files ] Model Constr. + Predicative Part

Both of these papers were published in `Studies in Logic and the
Foundations of Mathematics, 1975`. "An Intuitionistic*" seems to
be marginally different with respect to the 1972 version.

Peter Hancock has to be thanked for helping me tracking these
down.
Merge pull request #1 from gallais/master

[ 2 new files ] Model Constr. + Predicative Part