[pidhash] [0/4] patch series vs. 2.5.50-mm1

This is a series of patches against 2.5.50-mm1. 
They primarily have to do with pidhashing mechanisms, converting
some less-important users to the new API and eliminating some
tasklist iterations not covered by the original pidhash patches.

These should apply to 2.5.50-CURRENT; 2.5.50-mm1 includes bk snapshots.

mm1-2.5.50-2 [1/4] Make __do_SAK() use for_each_task_pid().
	The tty invariant involving ->tty being strictly associated
	with ->session has long been established. This converts
	__do_SAK() to use the pidhashing instead of iteration over
	the global tasklist.
mm1-2.5.50-5 [2/4] cap_set_pg() uses do_each_thread() to search for
	tasks in a given pgrp; convert it to for_each_task_pid()
wli-2.5.50-3 [3/5] eliminate proc_fill_super() tasklist iteration by
	means of introducing a nr_processes() per-cpu counter.
wli-2.5.50-6 [4/4] make get_pid_list() scan the PID bitmap instead of
	the tasklist.

Tested on 16x/16GB NUMA-Q with up to 16384 distinct processes.

Bill