coding guidelines: prefer use of instead of

Functionally equivalent, but more modern.  This is also what Google's C++
Style Guide says.

Author: Daniel Kroening

CODING_STANDARD.md

@@ -160,7 +160,7 @@ Formatting is enforced using clang-format. For more information about this, see
 
 # C++ features
 - Do not use namespaces, except for anonymous namespaces.
-- Prefer use of `typedef` instead of `using`.
+- Prefer use of `using` instead of `typedef`.
 - Prefer use of `class` instead of `struct`.
 - Write type modifiers before the type specifier.
 - Make references `const` whenever possible