codec_filter_set_ms_from_bc: prepare for CSD

In all the places where codec_filter_ functions get called, for CSD we
will need to filter the bearer services. Add a new
transaction_cc.c file for functions that either combine the
codec_filter_ function with logic for CSD and voice calls or just call
the existing codec_filter function and a new csd_filter function.

Start with moving codec_filter_set_ms_from_bc to this new file, it will
be extended with a case for CSD in a future patch.

Related: OS#4394
Change-Id: If225f2a299ce6bc9ae35a17d6f591d889f49155e
diff --git a/include/osmocom/msc/Makefile.am b/include/osmocom/msc/Makefile.am
index 34b4902..948021a 100644
--- a/include/osmocom/msc/Makefile.am
+++ b/include/osmocom/msc/Makefile.am
@@ -49,6 +49,7 @@
 	silent_call.h \
 	sms_queue.h \
 	transaction.h \
+	transaction_cc.h \
 	vlr.h \
 	vlr_sgs.h \
 	vty.h \