library: Initial work on GPRS RLC/MAC encoder/decoder

For Downlink and Uplink RLC/MAC Control blocks this is already working
quite nicely.  Data blocks is not working, as their encoding cannot be
expressed in TTCN-3 RAW syntax, and a mixture of C++/native and
RAW-generated coder will be required.
diff --git a/library/GSM_Types.ttcn b/library/GSM_Types.ttcn
index c205140..7275101 100644
--- a/library/GSM_Types.ttcn
+++ b/library/GSM_Types.ttcn
@@ -16,6 +16,7 @@
 	type integer GsmRxLev (0..63);
 	type integer GsmTsc (0..7) with { variant "FIELDLENGTH(8)" };
 	type uint32_t GsmTmsi;
+	type uint32_t GprsTlli;
 
 	/* Table 10.4.1 of Section 10.4 / 3GPP TS 44.018 */
 	type enumerated RrMessageType {
@@ -149,6 +150,9 @@
 	type record MaioHsn {
 	} with { variant "" };
 
+	/* TS 24.008 10.5.1.1 */
+	type uint16_t CellIdentity;
+
 	/* TS 24.008 10.5.1.2 */
 	type uint4_t CipheringKeySeqNr (0..7);
 
@@ -335,6 +339,21 @@
 		boolean	ps_ir
 	} with { variant "" };
 
+	/* 24.008 10.5.5.6 */
+	type record DrxParameter {
+		uint8_t		split_pg_cycle_code,
+		uint4_t		drx_cycle_len_coeff,
+		boolean		split_on_ccch,
+		uint3_t		non_drx_timer
+	} with { variant "" };
+
+	/* 24.008 10.5.5.15 */
+	type record RoutingAreaIdentification {
+		LocationAreaIdentification	lai,
+		uint8_t				rac
+	} with { variant "" };
+
+
 
 	/* 9.1.18 */
 	type record ImmediateAssignment {