ECL output-files semantics has changed, so unintern the old one rather than conflict.
Rename *compile-op-compile-file-function* to just *compile-file-function*.
Factor all the lisp build perform's through perform-lisp-FOO,
so they can be shared with concatenated targets that are not cl-source-file
without fighting default methods and class inheritance.

Also, fix make-pathname* to make CLISP happy.
Uniformly use "backward-compat*" in comments.
Rename operation-forced{,-not}-p to action-forced-p.
Shuffle some functions around.
Refactor operate into an :around and a regular method.