Add a terminal message for the crash strangler

src/pocketmine/Server.php

@@ -2254,6 +2254,7 @@ class Server{
 		//Force minimum uptime to be >= 120 seconds, to reduce the impact of spammy crash loops
 		$spacing = ((int) \pocketmine\START_TIME) - time() + 120;
 		if($spacing > 0){
+			echo "--- Waiting $spacing seconds to throttle automatic restart (you can kill the process safely now) ---" . PHP_EOL;
 			sleep($spacing);
 		}
 		@Utils::kill(getmypid());