RFC: "nice" is per process

When splitting appart the process structure for theads, I made a mistake
and made the "nice" value a property of the ksegrp. This is wrong
because Posix specifies that Nice always affects the entire process,
so this patch moves it back to the process. This does not mean that all
threads will have the same priority, only that the nice value used to
influence their priority will be the same throughout the process.


comments?

I've sent this to several people without comment so i'm widenning the 
request group.

julian