Congtribute some patch 

1. Handle negative escaped time
This can be occurred when some one change server's local time
2. Add ignore option for changing keep-alive check dynamically!
Give flexiable configration for client keep-alive mechanism
3. Use server's time for all the client's timestamp, so we can give up NTP Server
In most ENV, there is no condition to build a ntp server.
Any MORE, We can just correct server's time enough if we use this patch