Merge package.el, written by Tom Tromey <tromey@redhat.com>.

Merge package.el, written by Tom Tromey <tromey@redhat.com>.
Changes relative to version 0.9 of package.el are listed below:

* emacs-lisp/package-x.el: New file.  Package uploading
functionality split out from package.el.

* emacs-lisp/package.el (package-archive-base): Point to
elpa.gnu.org.
(package-enable, package-load-list): New defcustoms.
(package-user-dir, package-directory-list): Turn into defcustoms.
Don't include package-user-dir in package-directory-list.
(package--builtins-base): Don't include Emacs as a "package".
(package-subdirectory-regexp): New var.
(package-load-all-descriptors, package-compute-transaction)
(package-download-transaction): Obey package-load-list.
(package-activate-1): Rename from package-do-activate.
(package-list-packages-internal): Check package-load-list.
(package-load-descriptor, package-generate-autoloads)
(package-unpack, package-unpack-single)
(package--read-archive-file, package-delete): Use
expand-file-name.

* startup.el (command-line): Load packages after reading init
file.