libbsc: Add ctrl command for MNC, MCC, short-name and long-name

Add the framework for adding more setting commands.
diff --git a/openbsc/include/openbsc/gsm_data.h b/openbsc/include/openbsc/gsm_data.h
index 404dfe4..1b4720f 100644
--- a/openbsc/include/openbsc/gsm_data.h
+++ b/openbsc/include/openbsc/gsm_data.h
@@ -433,4 +433,7 @@
 extern const struct value_string bts_type_names[_NUM_GSM_BTS_TYPE+1];
 extern const struct value_string bts_type_descs[_NUM_GSM_BTS_TYPE+1];
 
+/* control interface handling */
+int bsc_base_ctrl_cmds_install(void);
+
 #endif /* _GSM_DATA_H */