Move SIGUSR1 notification as late as possible.

If we inherited a signal mask from the parent process that ignores SIGUSR1,
then we will send SIGUSR1 to the parent to indicate when we're ready to
accept connections.  Unfortunately, we send this notification way too
early, right after creating the sockets rather than just before entering
the main loop.

Move it to just before Dispatch() so we're not lying quite so much.

dix/main.c

@@ -449,6 +449,8 @@ main(int argc, char *argv[], char *envp[])
 	    }
 	}
 
+	NotifyParentProcess();
+
 	Dispatch();
 
 	/* Now free up whatever must be freed */