2.26.61: Upgrade tweak for ECL. Small refactoring for lisp-build.

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.