locitest: generate tests from the test_data files

The "c" section of the test data file should allocate and populate a LOCI
object. The resulting wire buffer is compared to the "binary" section.

This only tests serialization, but given that we have autogenerated tests that
round-trip each object I think this is sufficient.

I added C sections to the OF 1.0 test data files. OF 1.3 tests will come in a
future pull request.
diff --git a/c_gen/templates/locitest/main.c b/c_gen/templates/locitest/main.c
index 3b24035..86f7ae6 100644
--- a/c_gen/templates/locitest/main.c
+++ b/c_gen/templates/locitest/main.c
@@ -41,5 +41,7 @@
 
     RUN_TEST(ext_objs);
 
+    TEST_ASSERT(test_datafiles() == TEST_PASS);
+
     return global_error;
 }