Allow anonymous namespaces

I gather that this language feature is allowed, but it isn't used.
Perhaps if it's clearer that it's allowed in the coding standard
then people will realise they can use it.

CODING_STANDARD

@@ -122,7 +122,7 @@ Program Command Line Options
   from the command line into the options
 
 C++ features:
-- Do not use namespaces.
+- Do not use namespaces, except for anonymous namespaces.
 - Prefer use of 'typedef' insted of 'using'.
 - Prefer use of 'class' instead of 'struct'.
 - Write type modifiers before the type specifier.