add namespaces to C (in my local clang) OR "tag" a couple of functions

Hi.

(In my local clang copy) I would like to "tag" a bunch of C/C++
functions/globals with some additional string/attribute.

As I am not yet very experienced with hacking clang, I'd appreciate your
comment whether one of the following approaches achievable without hacking
clang too much.

Way 1