* pinfo.cc (winpids:add): New method.

* pinfo.cc (winpids:add): New method.
(winpids::enumNT): New method renamed from EnumProcessesNT.  Use add method to
add elements to the lists.
(winpids::enum9x): New method renamed from EnumProcesses9x.  Use add method to
add elements to the lists.
(winpids::enum_init): Accept 'winpid' parameter to control whether to add all
windows pids to the list.
(winpids::release): New method.
* pinfo.h (winpids): Reflect above changes.
* signal.cc (kill_pgrp): Ditto.
* external.cc (fillout_pinfo): Ditto.