bts: Extend Osmocom-specific RSL "supplementary meas info IE"

In osmo-bts Change-Id Iea4a4781481f77c6163d82dcd71a844a5be87bf2
we introduce an Osmocom specific "supplementary measurement info IE"
into the RSL MEAS REP message.  This commit adds the related type
definitions and extends the related matching in BTS_Tests.ttcn.

Change-Id: I5d1114c73508c67ad7cd9864d7370367612b1241
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 1044747..b77a70a 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -1240,8 +1240,13 @@
 		supp_meas_info := omit
 	};
 	if (l1p.toa256_enabled) {
-		ul_meas.len := 5;
-		ul_meas.supp_meas_info := int2oct(l1p.timing_offset_256syms, 2);
+		ul_meas.len := (3+8);
+		ul_meas.supp_meas_info := {
+			toa256_mean := l1p.timing_offset_256syms,
+			toa256_min := ?,
+			toa256_max := ?,
+			toa256_std_dev := ?
+		}
 	}
 	/* HACK HACK HACK FIXME HACK HACK HACK see https://osmocom.org/issues/2988 */
 	ul_meas.rxlev_f_u := ?;