THRIFT-2404 emit warning on (typically inefficient) list<byte>

Patch: Jens Geyer
diff --git a/compiler/cpp/src/main.h b/compiler/cpp/src/main.h
index 87af5f6..f737e3f 100644
--- a/compiler/cpp/src/main.h
+++ b/compiler/cpp/src/main.h
@@ -88,6 +88,10 @@
  */
 void declare_valid_program_doctext();
 
+/**
+ * Emits a warning on list<byte>, binary type is typically a much better choice.
+ */
+void check_for_list_of_bytes(t_type* list_elem_type);
 
 /**
  * Flex utilities