fact: Definition square_functor_pfiber {A B C D} {f : A ->* B} {g : C ->* D} {h : A ->* C} {k : B ->* D} (p : k o* f ==* g o* h) : h o* pfib f ==* pfib g o* functor_pfiber p.
imports: Basics Types WildCat HFiber Pointed.Core Pointed.pEquiv Pointed.Loops