[Groff] Copyright issues

[Werner LEMBERG]

Folks,


I've added/updated a lot of copyright messages to files in the groff
bundle; this process is not finished yet.  For the moment, I use GPL2
(in case it is GPLed), trying to stay with a constant format so that a
script will finally convert those strings to GPL3.  Smaller files,
notably `README's and friends, get a simpler, public-domain like
license.

For simplicity, I've done that for the stuff in the `contrib'
subdirectory also -- all contributors are asked to check the changes
and provide patches in case I've done something wrong.


    Werner