gsm_04_08: Add a operation to enable ciphering on a lchan

This will take care of the auth/check/enable cipher sequence
and call a callback function when done.

Currently the negotiated Kc is saved but not re-used, so
there is an authentication each time ...

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/openbsc/src/Makefile.am b/openbsc/src/Makefile.am
index d5d0068..03f62ab 100644
--- a/openbsc/src/Makefile.am
+++ b/openbsc/src/Makefile.am
@@ -23,7 +23,7 @@
 libmsc_a_SOURCES = gsm_subscriber.c db.c \
 		mncc.c gsm_04_08.c gsm_04_11.c transaction.c \
 		token_auth.c rrlp.c gsm_04_80.c ussd.c silent_call.c \
-		handover_logic.c handover_decision.c meas_rep.c
+		handover_logic.c handover_decision.c meas_rep.c auth.c
 
 libvty_a_SOURCES = common_vty.c