* The tunnel manager are now thre mode : disable, enable and auto
* Two new functions: linphone_tunnel_set_mode() and linphone_tunnel_get_mode()
* linphone_tunnel_enable(), linphone_tunnel_enabled(), linphone_tunnel_auto_detect()
and linphone_tunnel_auto_detect_enabled() are now deprecated.
If this parameter is set to 1, SIP packets will pass through tunnels when the
tunnel mode is enabled. If set to 0, SIP packets will be directly sent to proxies
whatever the state of tunnels