Conflicts:
src/mme/mme_s11_handler.h

You can find the usage nas_message_test8 in test/nas_message_test.c

update nas_message.py for supporting detach message

2. modify nas_message.py
3. store generated cache file

Now, we'll use 10.1.35.x network for loopback test

- sudo ip tuntap add name pgwtun mode tun
- sudo ./scripts/netconfig.sh

After then,
- ./test/...

Conflicts:
src/pgw/pgw_context.c
src/pgw/pgw_path.c

PGW : Forward GTP-U pakcets to tuntap interface

Later, we need to verify another value.

from : if (size > (p->clbuf->size - headroom))
to : if (size >= (p->clbuf->size - headroom))