library: remove an arbitrary pid/uid limit, <pids> api

That arbitrary limit to selecting tasks via pid or uid
has been present since a first blush effort referenced
below. Back then, our current select function required
use of three functions: 'alloc', 'fill' and 'dealloc'.

In any case, that FILL_ID_MAX has been proven to cause
problems for ps reflected in an issue also seen below.

This commit simply removes that arbitrary upper limit.

[ we've gone the extra distance of allocating memory ]
[ then copying user pids/uids since a pids list must ]
[ end in zero while neither user list was delimited. ]

Reference(s):
#387


. Aug, 2015 - implement new task/thread api
commit 7e6a371d

Signed-off-by: Jim Warner <james.warner@comcast.net>