Add two utility functions to function_list.

src/function_list.c

@@ -9,6 +9,14 @@ libab_result libab_function_list_insert(libab_function_list* list,
     return libab_ref_vec_insert(&list->functions, function);
 }
 
+size_t libab_function_list_size(libab_function_list* list) {
+    return list->functions.size;
+}
+
+void libab_function_list_index(libab_function_list* list, size_t index, libab_ref* into) {
+    libab_ref_vec_index(&list->functions, index, into);
+}
+
 void libab_function_list_free(libab_function_list* list) {
     libab_ref_vec_free(&list->functions);
 }