remove unused patches
Add patch to:
Automatically detect whether Curve25519 is available in NSS for USE_DH31

Signed-off-by: Antony Antony <antony@phenome.org>

remove building kernel module, it is not used and is not working with 4.19

rework the ready to use l2tp-ipsec example

Signed-off-by: Lucian Cristian <lucian.cristian@gmail.com>