2.26.142: Update the system definitions.
A better asdf.asd. Refactor the preloaded system mechanism, use it for cl-launch 3.21.2. Rename bundle-pathname to build-pathname, move it from bundle-system to system. Rename the gcl<2.7 feature gcl2.6. Die on gcl2.5 and earlier. Don't even try to compile-file asdf using gcl 2.6, just load the .lisp. Rename asdf/compatibility to asdf/common-lisp, exporting only CL symbols. Fix define-package to correctly handle exporting of NIL. Also, make it work with Genera, with #'(lambda instead of (lambda, and using lisp:loop (via a macro loop*) when destructuring is required. Document more 2.27 changes in changelog. If there is no :pathname and no load-pathname, do NOT have a system pathname take defaults from *default-pathname-defaults*, but make it NIL.