* exceptions.cc (set_signal_mask): Report on input argument rather than

getsigmask.
* fhandler.h (fhandler_base): Make friends with close_all_files.
* pinfo.cc (_pinfo::set_ctty): Add more debugging.
* sigproc.cc (proc_can_be_signalled): Detect state when signal handler thread
is gone in target process as an EPERM situation.  Set errno to ESRCH if process
doesn't exist.
(sigproc_terminate): Set sendsig to illegal value when closed.
(sig_send): Rely on proc_can_be_signalled setting the proper errno.
* syscalls.cc (close_all_files): Detect when all ttys are closed prior to
calling close_all_files.  The ctty needs to be closed explicitly in this case.

winsup/cygwin/exceptions.cc

@@ -978,7 +978,7 @@ set_signal_mask (sigset_t newmask, sigset_t& oldmask)
 {
   mask_sync->acquire (INFINITE);
   newmask &= ~SIG_NONMASKABLE;
-  sigproc_printf ("old mask = %x, new mask = %x", myself->getsigmask (), newmask);
+  sigproc_printf ("old mask %p, new mask %p", oldmask, newmask);
   myself->setsigmask (newmask);	// Set a new mask
   mask_sync->release ();
   if (oldmask & ~newmask)