Add xref Makefile target

Move src/ibrowse_test.erl file to the test directory.

Makefile

@@ -13,8 +13,10 @@ install: all
 test: all
 	./rebar eunit
 	(cd test; make) 
-	erl -noshell -pa ebin -pa test -s ibrowse -s ibrowse_test unit_tests \
+	erl -noshell -pa .eunit -pa test -s ibrowse -s ibrowse_test unit_tests \
 	-s ibrowse_test verify_chunked_streaming \
 	-s ibrowse_test test_chunked_streaming_once \
 	-s erlang halt
 
+xref: all
+	./rebar xref

rebar.config

@@ -1,2 +1,3 @@
 {erl_opts, [debug_info, warn_unused_vars, nowarn_shadow_vars, warn_unused_import]}.
-{eunit_opts, [verbose]}.
+{xref_checks, [undefined_function_calls, deprecated_function_calls]}.
+{eunit_opts, [verbose]}.