Added an interface for kernel event listeners.

src/libcharon/Makefile.am

@@ -41,6 +41,7 @@ encoding/payloads/vendor_id_payload.c encoding/payloads/vendor_id_payload.h \
 kernel/kernel_interface.c kernel/kernel_interface.h \
 kernel/kernel_ipsec.c kernel/kernel_ipsec.h \
 kernel/kernel_net.h \
+kernel/kernel_listener.h \
 network/packet.c network/packet.h \
 network/receiver.c network/receiver.h \
 network/sender.c network/sender.h \