* emacs/guix-base.el (guix-switch-to-generation): New procedure.
* emacs/guix-info.el (guix-generation-info-insert-current): Insert button for
switching to generation.
* emacs/guix-list.el (guix-generation-list-switch): New procedure.
* doc/emacs.texi (emacs List buffer, emacs Info buffer): Document switching
generations.
* doc/emacs.texi (emacs List buffer): Mention new key bindings.
* emacs/guix-base.el (guix-delete-generations): New procedure.
* emacs/guix-info.el (guix-generation-info-insert-number): Use it.
* emacs/guix-list.el (guix-generation-list-mark-delete,
guix-generation-list-execute): New procedures.
* emacs/guix-main.scm (delete-generations*): New procedure.
Use "U" to upgrade the current package, "^" to upgrade all.
* emacs/guix-list.el: (guix-list-unmark): With prefix, mark all.
(guix-package-list-mark-outputs): New procedure.
(guix-package-list-mark-install, guix-package-list-mark-delete)
(guix-package-list-mark-upgrade): Use it.
(guix-package-list-mark-upgrades): New command.
* doc/emacs.texi (emacs List buffer): Update the manual accordingly.
* configure.ac (emacsuidir): New variable.
(AC_CONFIG_FILES): Add 'emacs/guix-init.el', 'emacs/guix-helper.scm'.
* Makefile.am: Include 'emacs.am'.
* emacs.am: New file.
* doc/emacs.texi: New file.
* doc/guix.texi: Include 'emacs.texi'.
* emacs/guix-backend.el: New file.
* emacs/guix-base.el: New file.
* emacs/guix-helper.scm.in: New file.
* emacs/guix-history.el: New file.
* emacs/guix-info.el: New file.
* emacs/guix-init.el.in: New file.
* emacs/guix-list.el: New file.
* emacs/guix-main.scm: New file.
* emacs/guix-utils.el: New file.
* emacs/guix.el: New file.