* child_info. (CURR_CHILD_INFO_MAGIC): Refresh.

* child_info.  (CURR_CHILD_INFO_MAGIC): Refresh.
(child_info::child_info()): New constructor.
(child_info_spawn::child_info_spawn()): Ditto.
(child_info_spawn::operator new): New operator.
(child_info_spawn::set): New function.
* spawn.cc (av()): New constructor.
(av::operator new): New operator.
(av::set): New function.
(spawn_guts): Reorganize so that classes which allocates are defined early in
the function so that it can be properly cleaned up after an efault.  Set errno
to E2BIG in the event of a SEGV situation.