* dcrt0.cc (do_exit): Don't bother looking for pgrp children to send SIGHUP if

* dcrt0.cc (do_exit): Don't bother looking for pgrp children to send SIGHUP if
process has never created any children.
* fork.cc (fork): Set flag indicating that there is another process with our
process group.
* spawn.cc (spawn_guts): Ditto.
* pinfo.h (set_has_pgid_children): New methods for setting when process has
children in its process group.
* syscalls.cc (setpgid): Clear has_gid_children if pgid changes.