L1CTL: Add message segmentation helper via getMsgLen()

As L1CTL is using a stream socket, we need to give the UNIX_DOMAIN
port some clue as to where our L1CTL message boundaries are in the
stream.

This requires a patched UNIX_DOMAIN_SOCKETasp test port with the
following commit applied:

commit 655cb4ab2ac006b3a73d1b679c83081d9743410a
Author: Harald Welte <laforge@gnumonks.org>
Date:   Sun Feb 25 23:25:46 2018 +0100

    Add "getMsgLen" function similar to IPL4asp_PT

Change-Id: Iab33f57cb4311180e521a76307a552d16287b062
diff --git a/gprs_gb/gen_links.sh b/gprs_gb/gen_links.sh
index 5cbaaae..54d2bdd 100755
--- a/gprs_gb/gen_links.sh
+++ b/gprs_gb/gen_links.sh
@@ -53,7 +53,7 @@
 
 
 DIR=../library
-FILES="General_Types.ttcn GSM_Types.ttcn GSM_RR_Types.ttcn Osmocom_Types.ttcn RLCMAC_Types.ttcn RLCMAC_CSN1_Types.ttcn RLCMAC_EncDec.cc L1CTL_Types.ttcn L1CTL_PortType.ttcn LAPDm_RAW_PT.ttcn LAPDm_Types.ttcn "
+FILES="General_Types.ttcn GSM_Types.ttcn GSM_RR_Types.ttcn Osmocom_Types.ttcn RLCMAC_Types.ttcn RLCMAC_CSN1_Types.ttcn RLCMAC_EncDec.cc L1CTL_Types.ttcn L1CTL_PortType.ttcn L1CTL_PortType_CtrlFunct.ttcn L1CTL_PortType_CtrlFunctDef.cc LAPDm_RAW_PT.ttcn LAPDm_Types.ttcn "
 FILES+="NS_Emulation.ttcn NS_CodecPort.ttcn NS_CodecPort_CtrlFunct.ttcn NS_CodecPort_CtrlFunctDef.cc "
 FILES+="BSSGP_Emulation.ttcn Osmocom_Gb_Types.ttcn "
 FILES+="LLC_Templates.ttcn L3_Templates.ttcn L3_Common.ttcn "