Cleanups done or initiated during the ASDF Walkthrough.
* load-op needn't be sideway, its sideway dependencies are already provided by prepare-op * compile-op should use compile-op (default) not load-op as its downward-operation. * no need for an input-files method for prepare-op, nil is the global default. * Some documentation for compute-action-stamp. * Don't skip upgrade from 1.x on Allegro anymore, since we now correctly punt. * Instead of asdf/package:define-package, use the canonical name uiop/package:define-package