[sudo-users] sudo v1.7.1 runas group allows runas any user

[Blazejewski Marcin-AMB107]

> 
> I think the following should cover all the bases.  It also fixes
> the output of "sudo -l" for group-only entries.  I made it print
> the user's name as the runas user instead of leaving the user blank
> because I find it easier to read that way, though I could be persuaded
> to change that.
> 

Works great now, thanks a lot!

Marcin