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/src/gprs/Makefile.am b/openbsc/src/gprs/Makefile.am
index c044f24..3970ba6 100644
--- a/openbsc/src/gprs/Makefile.am
+++ b/openbsc/src/gprs/Makefile.am
@@ -93,6 +93,7 @@
 	oap.c \
 	oap_messages.c \
 	gprs_llc_xid.c \
+	v42bis.c \
 	$(NULL)
 osmo_sgsn_LDADD = \
 	$(top_builddir)/src/libcommon/libcommon.a \