* lisp/emacs-lisp/package.el: Don't recompute dir. Use pkg-descs more.

* lisp/emacs-lisp/package.el: Don't recompute dir.  Use pkg-descs more.
(package-desc): Add `dir' field.
(package-desc-full-name): New function.
(package-load-descriptor): Combine the two arguments.  Don't use `load'.
(package-maybe-load-descriptor): Remove.
(package-load-all-descriptors): Just call package-load-descriptor.
(package--disabled-p): New function.
(package-desc-vers, package-desc-doc): Remove aliases.
(package--dir): Remove function.
(package-activate): Check if a package is disabled.
(package-process-define-package): New function, extracted from
define-package.
(define-package): Turn into a place holder.
(package-unpack-single, package-tar-file-info):
Use package--description-file.
(package-compute-transaction): Use package--disabled-p.
(package-download-transaction): Don't call
package-maybe-load-descriptor since they're all loaded anyway.
(package-install): Change argument to be a pkg-desc.
(package-delete): Use a single pkg-desc argument.
(describe-package-1): Use package-desc-dir instead of package--dir.
Use package-desc property instead of package-symbol.
(package-install-button-action): Adjust accordingly.
(package--push): Rewrite.
(package-menu--print-info): Adjust accordingly.  Change the ID format
to be a pkg-desc.
(package-menu-describe-package, package-menu-get-status)
(package-menu--find-upgrades, package-menu-mark-upgrades)
(package-menu-execute, package-menu--name-predicate):
Adjust accordingly.
* lisp/startup.el (package--description-file): New function.
(command-line): Use it.
* lisp/emacs-lisp/package-x.el (package-upload-buffer-internal):
Use package-desc-version.