* cygheap.h (init_cygheap): Play more vfork shell games and move ctty_on_hold

and open_fhs_on_hold (back) here.
* dcrt0.cc (_dll_crt0): Just set impure_ptr_ptr here and let later
initialization deal with tls.
* dtable.cc (dtable::vfork_child_fixup): Move ctty considerations here.
(dtable:vfork_parent_restore): And here.
* fork.cc (vfork): Reflect change to ctty handling.
* perthread.h (vfork_save::fhctty): Eliminate.
* cygwin.din: Make more exports NOSIGFE that will never be interrupted by a
signal.
* init.cc (dll_entry): Set stackptr to NULL to catch problems earlier.

winsup/cygwin/dcrt0.cc

@@ -916,12 +916,11 @@ _dll_crt0 ()
 void
 dll_crt0 (per_process *uptr)
 {
-  char padding[CYGTLS_PADSIZE];
   /* Set the local copy of the pointer into the user space. */
   if (uptr && uptr != user_data)
     {
       memcpy (user_data, uptr, per_process_overwrite);
-      *(user_data->impure_ptr_ptr) = initialize_main_tls (padding);
+      *(user_data->impure_ptr_ptr) = &reent_data;
     }
   _dll_crt0 ();
 }