Add hand-written encoder/decoder for RLC/MAC UL/DL data blocks

Their format is simply too complex to be used with the automatic RAW
encoder/decoder.  Let's implement it by hand, using the automatic
coder whenever possible.
diff --git a/gprs_gb/gen_links.sh b/gprs_gb/gen_links.sh
index 20b40be..e939690 100755
--- a/gprs_gb/gen_links.sh
+++ b/gprs_gb/gen_links.sh
@@ -30,5 +30,5 @@
 
 
 DIR=../library
-FILES="General_Types.ttcn GSM_Types.ttcn GSM_RR_Types.ttcn Osmocom_Types.ttcn RLCMAC_Types.ttcn L1CTL_Types.ttcn L1CTL_PortType.ttcn"
+FILES="General_Types.ttcn GSM_Types.ttcn GSM_RR_Types.ttcn Osmocom_Types.ttcn RLCMAC_Types.ttcn RLCMAC_EncDec.cc L1CTL_Types.ttcn L1CTL_PortType.ttcn"
 gen_links $DIR $FILES