Merge branch 'channel_destroy' of ssh://gnunet.org/gnunet into channel_destroy

diff --cc src/cadet/cadet_api.c
Simple merge

diff --cc src/cadet/gnunet-service-cadet_channel.c
Simple merge

diff --cc src/cadet/gnunet-service-cadet_tunnels.c
Simple merge

diff --cc src/include/gnunet_protocols.h
Simple merge