* lisp/emacs-lisp/package.el: Don't activate packages older than builtin.

* lisp/emacs-lisp/package.el: Don't activate packages older than builtin.
(package-obsolete-list): Rename from package-obsolete-alist, and make
it into a simple list of package-desc.
(package-strip-version): Remove.
(package-built-in-p): Use package--builtin-versions.
(package-mark-obsolete): Simplify.
(package-process-define-package): Mark it obsolete if older than the
builtin version.
(package-handle-response): Use line-end-position.
(package-read-archive-contents, package--download-one-archive):
Simplify.
(package--add-to-archive-contents): Skip if older than the builtin or
installed version.
(package-menu-describe-package): Fix last change.
(package-list-unversioned): New var.
(package-menu--generate): Use it.

* lisp/Makefile.in (autoloads): Set autoload-builtin-package-versions.

* lisp/startup.el (package--builtin-versions): New var.
(package-subdirectory-regexp): Remove.
(package--description-file): Hard code its value instead.

* lisp/emacs-lisp/autoload.el: Manage package--builtin-versions.
(autoload--insert-text, autoload--insert-cookie-text): New functions.
(autoload-builtin-package-versions): New variable.
(autoload-generate-file-autoloads): Use them.
Remove the list of autoloaded functions/macros from the
(autoload...) comments.