* external.cc (fillout_pinfo): Pass PID_NOREDIR flag to pinfo init to avoid

* external.cc (fillout_pinfo): Pass PID_NOREDIR flag to pinfo init to avoid
finding execed processes twice.
* signal.cc (kill_pgrp): Ditto.
* spawn.cc (spawn_guts): Avoid passing first argument to CreateProcess when
running a windows shell so that CreateProcess will locate the shell.
Reorganize so that correct error is returned when CreateProcess fails.