RFC: removal of share/doc/{papers,psd,smm,usd} in 2 months

Hi all,

those roff sources have been very naughty and will be removed from the
tree by the end of the year. Most of those papers are severely out of
date and provide no more use to the system. They can probably also be
found online using a search engine of your choice.

Should people feel strongly about them, we might be able to move them
over to the doc repository.

Thanks
Uli