Add initial CSD support with external MNCC

Implement and use CSD bearer service logic (with similar audio codec code):
* csd_filter (codec_filter)
* csd_bs (sdp_audio_codec)
* csd_bs_list (sdp_audio_codecs)

Related: OS#4394
Change-Id: Ide8b8321e0401dcbe35da2ec9cee0abca821d99a
diff --git a/include/osmocom/msc/Makefile.am b/include/osmocom/msc/Makefile.am
index 948021a..3286c37 100644
--- a/include/osmocom/msc/Makefile.am
+++ b/include/osmocom/msc/Makefile.am
@@ -3,6 +3,8 @@
 	cell_id_list.h \
 	codec_filter.h \
 	codec_mapping.h \
+	csd_bs.h \
+	csd_filter.h \
 	db.h \
 	debug.h \
 	e_link.h \