[codecs filter] add codec_filter.h,c

Add the infrastructure to store and filter all codec limitiations from
the different stages: MS, BSS, CN and remote call leg. Upcoming patches
will properly collect these and find an optimal codec.

No functional change, yet.

Related: SYS#5066
Change-Id: I4d90f7ca62f2307a7b93dd164aeecbf4bd98ff0a
diff --git a/include/osmocom/msc/Makefile.am b/include/osmocom/msc/Makefile.am
index 80f8972..34b4902 100644
--- a/include/osmocom/msc/Makefile.am
+++ b/include/osmocom/msc/Makefile.am
@@ -1,6 +1,7 @@
 noinst_HEADERS = \
 	call_leg.h \
 	cell_id_list.h \
+	codec_filter.h \
 	codec_mapping.h \
 	db.h \
 	debug.h \