Add TCP keepalive mechanism
Created by: Mickaelh51
PR about this ticket: https://groups.google.com/forum/#!topic/unimrcp/3NCglz4dpzs When mrcp client doesn't send TCP/FIN, unimrcp server can use TCP keepalive mechanism to detect idle session and destroy it cleanly https://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/