ranap_parse_lai(): Fix wrong BCD decoding for MNC. Add test.

Fix the ranap_parse_lai() part that decodes the MNC: place the *10 at the
proper MNC digit.

Add a comprehensive test for ranap_parse_lai() in test-helpers.c. Because
ranap_parse_lai() logs things, add test_common.c to test-helpers compilation
and an expected stderr output to test-helpers' testsuite.at def.
diff --git a/src/tests/Makefile.am b/src/tests/Makefile.am
index 739410b..0fd050f 100644
--- a/src/tests/Makefile.am
+++ b/src/tests/Makefile.am
@@ -7,7 +7,7 @@
 HNBAP_FILES = $(top_srcdir)/src/hnbap_common.c $(top_srcdir)/src/hnbap_decoder.c $(top_srcdir)/src/hnbap_encoder.c
 RUA_FILES = $(top_srcdir)/src/rua_common.c $(top_srcdir)/src/rua_decoder.c $(top_srcdir)/src/rua_encoder.c $(top_srcdir)/src/rua_msg_factory.c
 
-test_helpers_SOURCES = test-helpers.c
+test_helpers_SOURCES = test-helpers.c test_common.c
 test_helpers_LDADD = $(COMMON_LIBS) $(top_builddir)/src/libosmo-ranap.la
 
 test_hnbap_SOURCES = $(top_srcdir)/src/hnbap_common.c $(top_srcdir)/src/hnbap_decoder.c test-hnbap.c test_common.c