[RFC v17][PATCH 14/60] pids 4/7: Add target_pids parameter to alloc_pid()

[Serge E. Hallyn]

Quoting Oren Laadan (orenl at librato.com):
> From: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
> 
> This parameter is currently NULL, but will be used in a follow-on patch.

Note that patches 1-4 of the clone_with_pid() patchset should
also be useful if we decide to re-create process trees in-kernel
and not export clone_with_pid().  (Though maybe not immediately
applicable to Alexey's current kthread_run()-based approach).

-serge