* fork.cc (fork): Honor error return from sig_send. Don't continue with fork

if we couldn't suspend signals.
* sigproc.cc (sig_send): Set sigCONT event when we see __SIGNOHOLD.
(wait_sig): Remove holding_signals.  Create pipe with a buffer which will
theoretically cause blocking if there is nothing reading on the pipe.  Wait for
sigCONT at end of loop when we have a __SIGHOLD.

winsup/cygwin/fork.cc

@@ -507,7 +507,14 @@ fork ()
       return -1;
     }
 
-  sig_send (NULL, __SIGHOLD);
+  if (sig_send (NULL, __SIGHOLD))
+    {
+      if (exit_state)
+	Sleep (INFINITE);
+      set_errno (EAGAIN);
+      return -1;
+    }
+
   ischild = setjmp (grouped.ch.jmp);
 
   void *esp;