* exceptions.cc (interrupt_setup): Move actions from setup_handler to here.

* exceptions.cc (interrupt_setup): Move actions from setup_handler to here.
(setup_handler): Move actions after a successful interrupt to interrupt_setup.
* fork.cc (vfork): Augment debugging output.
* sigproc.cc (proc_subproc): Ditto.
* spawn.cc (spawn_guts): Ditto.  Correctly fill out progname when spawn
NO_WAIT.  Call signal handler when a signal arrives.
* sigproc.h: Declare a function.