Add missing "extern" prefix (Andreas Eversberg)

diff --git a/include/openbsc/e1_input.h b/include/openbsc/e1_input.h
index 6d5a0be..2752db6 100644
--- a/include/openbsc/e1_input.h
+++ b/include/openbsc/e1_input.h
@@ -150,7 +150,7 @@
 int ia_config_connect(struct gsm_bts *bts, struct sockaddr_in *sin);
 int ipaccess_setup(struct gsm_network *gsmnet);
 
-struct llist_head e1inp_driver_list;
-struct llist_head e1inp_line_list;
+extern struct llist_head e1inp_driver_list;
+extern struct llist_head e1inp_line_list;
 
 #endif /* _E1_INPUT_H */