RAN_Emulation: Modularize protocol support

The RAN_Emulation currently unconditionally provides BSSAP and MGCP support.
Let's re-structure the code so that support for those protocols is now
possible to enable/disable at compile time.

This patch is in preparation of introducing RANAP support in RAN_Emulation.

Change-Id: Id53ba3ff05f9946230e0e4a759245de14a0f9fbd
Related: OS#2856
diff --git a/msc/gen_links.sh b/msc/gen_links.sh
index a29118a..e4e142b 100755
--- a/msc/gen_links.sh
+++ b/msc/gen_links.sh
@@ -89,7 +89,7 @@
 FILES="Misc_Helpers.ttcn General_Types.ttcn GSM_Types.ttcn Osmocom_Types.ttcn MNCC_Types.ttcn MNCC_EncDec.cc MNCC_CodecPort.ttcn mncc.h MNCC_Emulation.ttcn Osmocom_VTY_Functions.ttcn Native_Functions.ttcn Native_FunctionDefs.cc "
 FILES+="IPA_Types.ttcn IPA_Emulation.ttcnpp IPA_CodecPort.ttcn IPA_CodecPort_CtrlFunct.ttcn IPA_CodecPort_CtrlFunctDef.cc GSUP_Types.ttcn GSUP_Emulation.ttcn "
 FILES+="Osmocom_CTRL_Types.ttcn Osmocom_CTRL_Functions.ttcn Osmocom_CTRL_Adapter.ttcn L3_Templates.ttcn L3_Common.ttcn "
-FILES+="RAN_Emulation.ttcn BSSAP_CodecPort.ttcn BSSMAP_Templates.ttcn RAN_Adapter.ttcn MGCP_Types.ttcn MGCP_Templates.ttcn MGCP_CodecPort_CtrlFunct.ttcn MGCP_Emulation.ttcn "
+FILES+="RAN_Emulation.ttcnpp BSSAP_CodecPort.ttcn BSSMAP_Templates.ttcn RAN_Adapter.ttcnpp MGCP_Types.ttcn MGCP_Templates.ttcn MGCP_CodecPort_CtrlFunct.ttcn MGCP_Emulation.ttcn "
 FILES+="RTP_CodecPort.ttcn RTP_CodecPort_CtrlFunctDef.cc "
 FILES+="MGCP_CodecPort.ttcn MGCP_CodecPort_CtrlFunctDef.cc "
 FILES+="SMPP_CodecPort.ttcn SMPP_CodecPort_CtrlFunct.ttcn SMPP_CodecPort_CtrlFunctDef.cc SMPP_Emulation.ttcn SMPP_Templates.ttcn "