net_server: Clients can now check if a service is running.

* Using the new kMsgIsServiceRunning command.

headers/private/net/NetServer.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2010, Haiku, Inc. All Rights Reserved.
+ * Copyright 2006-2015, Haiku, Inc. All Rights Reserved.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -20,6 +20,7 @@
 #define kMsgJoinNetwork				'JNnw'
 #define kMsgLeaveNetwork			'LVnw'
 #define kMsgAutoJoinNetwork			'AJnw'
+#define kMsgIsServiceRunning		'IRsv'
 
 
 #endif	// _NET_SERVER_H