[OpenAFS-Doc] pts_membership man page

[Jason Edgecombe]

I just submitted bug #124151to RT to add the system:ptsviewers verbage 
to the man page.

I read the whole pts_membership man page, and the PRIVILIGES section 
reads like bad stereo instructions. It's not very clear. I think that 
part could be much clearer, but I don't understand the privacy flags 
enough to rewrite it. I think a table would better communicate the info.

Any comments?

Thanks,
Jason