(_onreturn): New helper class.
(winpids:add): Remove copied stuff. Try to put process handle into pinfo in
question and use _onreturn class to control when to close it.
(winpids::release): Remove use of copied array. Free procinfo when hProc is
NULL. Otherwise call release and call CloseHandle on hProc.
* pinfo.h (winpids::copied): Remove throughout class.