V.42bis: integration and unit test

 - Edit previously committed V.42bis implementation to function
   outside IAXmodem.
 - Add unit test to verify the correct function of V.42bis

Change-Id: I689413f2541b6def0625ce6bd96f1f488f05f99d
diff --git a/openbsc/tests/Makefile.am b/openbsc/tests/Makefile.am
index 2e342e0..0ebd2e2 100644
--- a/openbsc/tests/Makefile.am
+++ b/openbsc/tests/Makefile.am
@@ -12,6 +12,7 @@
 	xid \
 	sndcp_xid \
 	slhc \
+	v42bis \
 	$(NULL)
 
 if BUILD_NAT