Adding easy stuff from GNU Emacs - what is the least that needs to be done?

[Mats Lidell]

Hi,

Suppose, for the discussion, there is a file in GNU Emacs that can be
added to XEmacs without any modifications. What would be the proper
way to do it? Just change so that it reads "This file is part of
XEmacs" and a "Synched up with: GNU Emacs ###" line?

If the package that the file is added to contains other files that are
GPLv2 or later. Must all files in the package be modified at that time
to GPLv3 or later even though they don't depend on the new file?

Yours
-- 
%% Mats