Keeping copyright notices up to date

[Mark Harig]

1. There are a number of Guile's files that have invalid copyright
notices because their years are listed as ranges, which is not
allowed, for example, the files guile/GNUmakefile and
guile/maint.mk.  The year range should be deleted and replaced
with a comma-separated list of years.

2. Have all files that have been changed had their copyright years
updated?  Emacs can be told to check for the year of the
copyright notice and will prompt the user when a file has been
changed in a year that is not included in the copyright notice.
One way to activate this feature is to add the following to your
Emacs initialization file:

  (add-hook 'before-save-hook 'copyright-update)

Then, each time a file that includes the string "Copyright (C)..."
is modified, the list of years will be checked to see if the current
year is included in the list.  If the current year is not listed, then
the Emacs user will be asked whether they want it added.  If
the user answers "yes", then a comma, a space, and the four
digits of the current year will be added to the copyright line.

According to the Emacs file NEWS.22, this feature for checking
and updating the copyright each time a file is saved has been
available since Emacs version 22.1, so any version after that
can use it.

Here is a description from the Info node "(texinfo) copying"
of the requirements for the format and content of the copyright
notice:

"The copyright notice itself has the following legally defined sequence:

    Copyright (C) YEARS COPYRIGHT-OWNER.

 The word `Copyright' must always be written in English, even if the
document is otherwise written in another language.  This is due to
international law.

 The list of years should include all years in which a version was
completed (even if it was released in a subsequent year).  Ranges are
not allowed; each year must be written out individually and in full,
separated by commas."

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