add handover.h file to Makefile.am to make distcheck happy
diff --git a/openbsc/include/openbsc/Makefile.am b/openbsc/include/openbsc/Makefile.am
index 161a9a6..27c88b7 100644
--- a/openbsc/include/openbsc/Makefile.am
+++ b/openbsc/include/openbsc/Makefile.am
@@ -5,4 +5,4 @@
gsm_utils.h ipaccess.h rs232.h openbscdefines.h rtp_proxy.h \
bsc_rll.h mncc.h talloc.h transaction.h ussd.h gsm_04_80.h \
silent_call.h mgcp.h meas_rep.h bitvec.h rest_octets.h \
- system_information.h
+ system_information.h handover.h