Throughout use myself->ppid_handle rather than parent_alive.

* child_info.h (child_info): Eliminate parent_alive.
* dcrt0.cc (dll_crt0_1): Call fork_init for debugging pid creation.
* fork.cc (fork_child): Reflect change to fixup_mmaps_after_fork arguments.
(slow_pid_reuse): New function to grab last 'n' pids to prevent pid reuse.
(fork_parent): Move last_fork_proc into slow_pid_reuse.  Handle fork_pids
debugging.  Eliminate unnecessary call to set_child_mmap_ptr.
(fork_init): New debugging function.
* mmap.cc (fixup_mmaps_after_fork): Renamed from recreate_mmaps_after_fork.
Rely on copied data after a fork.
(set_child_mmap_ptr): Eliminate.
* pinfo.h (_pinfo): Eliminate parent_alive, mmap_ptr and reflect above changes.
* spawn.cc (spawn_guts): Eliminate vestiges of "old way" of sending new hProc
to parent process.

winsup/cygwin/exceptions.cc

@@ -891,8 +891,8 @@ sig_handle_tty_stop (int sig)
       pinfo parent (myself->ppid);
       sig_send (parent, __SIGCHILDSTOPPED);
     }
-  sigproc_printf ("process %d stopped by signal %d, parent_alive %p",
-		  myself->pid, sig, parent_alive);
+  sigproc_printf ("process %d stopped by signal %d, myself->ppid_handle %p",
+		  myself->pid, sig, myself->ppid_handle);
   /* There is a small race here with the above two mutexes */
   SuspendThread (hMainThread);
   return;