IPA: Add support for IPAC_IDTAG_OSMO_RAND

this is a non-standard RAND value used by osmo-bsc_nat.  The change
requires us to also properly define the individual IpaCcmGetPart
with a one-byte length value at its start.
diff --git a/library/IPA_Types.ttcn b/library/IPA_Types.ttcn
index e0e7521..1cafd33 100644
--- a/library/IPA_Types.ttcn
+++ b/library/IPA_Types.ttcn
@@ -64,14 +64,16 @@
 	IPAC_IDTAG_SWVERSION	('05'H),
 	IPAC_IDTAG_IPADDR	('06'H),
 	IPAC_IDTAG_MACADDR	('07'H),
-	IPAC_IDTAG_UNIT		('08'H)
+	IPAC_IDTAG_UNIT		('08'H),
+	IPAC_IDTAG_OSMO_RAND	('23'H)
 } with { variant "FIELDLENGTH(8)" }
 
 
 type record IpaCcmGetPart {
-	uint8_t		one,
+	uint8_t		len,
 	IpaCcmIdTag	tag
-}
+} with { variant (len) "LENGTHTO(tag)" }
+
 type set of IpaCcmGetPart IpaCcmIdGet;
 
 type record IpaCcmRespPart {