SMPP: Implement SMPP Osmocom Estensions on MO-SMS

An ESME can now be configured in the VTY to enable osmocom-extensions,
which will add vendor-specific SMPP TLVs for RxLev/RxQual/ARFCN/IMEI and
transmit power to the SMPP DELIVER-SM message type.
diff --git a/openbsc/src/libmsc/smpp_smsc.h b/openbsc/src/libmsc/smpp_smsc.h
index be72a0c..e72f81f 100644
--- a/openbsc/src/libmsc/smpp_smsc.h
+++ b/openbsc/src/libmsc/smpp_smsc.h
@@ -60,6 +60,7 @@
 	char passwd[SMPP_PASSWD_LEN+1];
 	int default_route;
 	int deliver_src_imsi;
+	int osmocom_ext;
 	struct llist_head route_list;
 };