Pod-Functions requires that Pod-Escapes be built to build

Pod-Functions requires that Pod-Escapes be built to build

Discovered doing a parallel build on OpenBSD, reproducible elsewhere
with:

  ./Configure ... && make ext/Pod-Functions/pm_to_blib

While Pod-Escapes is a dependency of Pod-Simple, the Pod-Simple build
process doesn't require that Pod-Escapes already be built, while the
Pod-Functions build process does.