NAT H.323 0.4 (beta) for Linux kernel 2.6.15 released

The main new feature of this release is T.120 support. So chat, whiteboard, file transfer and other T.120 applications are supported.

The second new feature is a parameter "gkrouted_only" for ip_conntrack_h323 module. Normally, when an endpoint registers with a gatekeeper, calls from anywhere to this endpoint will be forwarded by Linux firewall. If you don't think this is safe and your gatekeeper supports proxy function (like GNUGK), you can set gkrouted_only to 1. Thus, only calls from the gatekeeper will be forwarded to the registered endpoint.

Change log:
1. Added support for T.120 channels
2. Added parameter gkrouted_only (suggested by Patrick McHardy)
3. Splitted ASN.1 code and data (suggested by Patrick McHardy)
4. Sort ASN.1 data to avoid forwarding declarations (suggested by Patrick McHardy)
5. Reset next TPKT data length in get_tpkt_data()