Add EFR support to TRAU muxer + test case

Decoding and encoding of FR and EFR TRAU frames are put into seperate
functions. CRC check is done to detect bad EFR TRAU frames.

The test case includes FR and EFR transcoding.

EFR support was tested with Nokia InSite BTS and Siemens BS11.
diff --git a/openbsc/src/libmsc/gsm_04_08.c b/openbsc/src/libmsc/gsm_04_08.c
index 3cfc455..6360393 100644
--- a/openbsc/src/libmsc/gsm_04_08.c
+++ b/openbsc/src/libmsc/gsm_04_08.c
@@ -2876,6 +2876,7 @@
 	case MNCC_FRAME_RECV:
 		return tch_recv_mncc(net, data->callref, 1);
 	case GSM_TCHF_FRAME:
+	case GSM_TCHF_FRAME_EFR:
 		/* Find callref */
 		trans = trans_find_by_callref(net, data->callref);
 		if (!trans) {