bug fixes:
 - Remove unreachable code path
 - exit: report if the exit command was killed
 - exit: fix race zombie reaper
 - conn_sock: allow watchdog messages through the notify socket proxy
 - seccomp: add support for seccomp notify

misc:
 - Add seccomp to build dependency

included patch removes unnecessary dependency of libdl and also allows a succesfull build
disabled for arc where libseccomp does not seem to be available

Signed-off-by: Oskari Rauta <oskari.rauta@gmail.com>

Patch fixing segfaults on nulls was removed due to patch's content being now included in conmon's source since containers/conmon@355dbf1

Signed-off-by: Oskari Rauta <oskari.rauta@gmail.com>

Signed-off-by: Oskari Rauta <oskari.rauta@gmail.com>