[O] bug#30310: Built-in Org mode not listed as installed package

[Glenn Morris]

Package: emacs,org-mode
Version: 25.3

emacs -Q -f list-packages

The built-in Org mode is not listed.
(This eg causes org-edna to be listed as uninstallable.)
Adding a Version: header comment to lisp/org/org.el would fix this.
(There was one prior to Emacs rev 8223b1d233.)
Obviously it would need to be kept in sync with org-version.el.

Ref: http://lists.gnu.org/r/emacs-devel/2018-01/msg00813.html