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/src/libmsc/Makefile.am b/src/libmsc/Makefile.am
index bde70c9..9577475 100644
--- a/src/libmsc/Makefile.am
+++ b/src/libmsc/Makefile.am
@@ -68,6 +68,7 @@
 	sms_queue.c \
 	smsc_vty.c \
 	transaction.c \
+	transaction_cc.c \
 	msc_net_init.c \
 	ctrl_commands.c \
 	sgs_iface.c \