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/configure.ac b/openbsc/configure.ac
index cebabdc..173c6c8 100644
--- a/openbsc/configure.ac
+++ b/openbsc/configure.ac
@@ -233,6 +233,7 @@
     tests/xid/Makefile
     tests/sndcp_xid/Makefile
     tests/slhc/Makefile
+    tests/v42bis/Makefile
     doc/Makefile
     doc/examples/Makefile
     Makefile)