Merge Finder and package-menu functionality.

Merge Finder and package-menu functionality.

* lisp/finder.el: Require `package'.
(finder-known-keywords): Tweak descriptions.  Retire `oop' keyword.
(finder-package-info): Var deleted.
(finder-keywords-hash, finder--builtins-alist): New vars.
(finder-compile-keywords): Compute package--builtins and
finder-keywords-hash instead of finder-keywords-hash, respecting
the "Package" header.
(finder-unknown-keywords, finder-list-matches): Use
finder-keywords-hash and package--list-packages.
(finder-mode): Don't set font-lock-defaults.
(finder-exit): We don't use "*Finder-package*" and "*Finder
Category*" buffers anymore.

* lisp/info.el (Info-finder-find-node): Search package-alist instead of
finder-package-info.

* lisp/emacs-lisp/package.el (package--builtins-base): Var deleted.
(package--builtins): Set default value to nil.
(package-initialize): Load precomputed value of package--builtins
from finder-inf.el.
(package-alist, package-compute-transaction)
(package-download-transaction): Improve docstring.
(package-read-all-archive-contents): Do not change
package--builtins here.
(list-packages): Make package-list-packages an alias for this.
Sort by status by default.
(package--list-packages): Add optional PACKAGES arg.
(describe-package-1): Use font-lock-face property.  For built-in
packages, insert file commentary.
(package--generate-package-list): Rename from
package-list-packages-internal; all callers changed.  Add optional
PACKAGES arg.  Add alphabetical sort fallbacks.
(package-menu--version-predicate, package-menu--status-predicate)
(package-menu--description-predicate)
(package-menu--name-predicate): New functions.