Add some basic tests for verifying json_object_equal behavior

Do some basic checks on ints, doubles, strings, arrays and "complex" objects.

.gitignore

@@ -45,6 +45,7 @@
 /tests/test_null
 /tests/test_printbuf
 /tests/test_set_serializer
+/tests/test_compare
 /tests/*.vg.out
 /tests/*.log
 /tests/*.trs