Copyright notices

[Eli Zaretskii]

Since it took me by surprise, I thought that maybe other maintainers
aren't aware of this text from maintain.texi, which says how to update
copyright years in the files' copyright notices:

    To update the list of year numbers, add each year in which you have
    made nontrivial changes to the package.  (Here we assume you're using
    a publicly accessible revision control server, so that every revision
    installed is also immediately and automatically published.)  When you
    add the new year, it is not required to keep track which files have
    seen significant changes in the new year and which have not.  It is
    recommended and simpler to add the new year to all files in the
    package, and be done with it for the rest of the year.

The last sentence is what took me by surprise, when Richard Stallman
asked people who work on Emacs to add 2006 to _all_ the files in the
distribution, regardless of whether they were modified in that year or
not.

Perhaps we should have a script to do the same once a year, and stop
worrying about updating the individual notices when we modify each
file.