How to use new extension (render_target)?

I’ve read EXT_render_target specification and I think it’s very useful, but I don’t know how to use it.
How to declare functions? Because there is no prototypes in glext.h. In the specification there is something like:


And I don’t know what number should it be.

Thanks for help.

It’s a draft. The extension is not even complete so there isn’t even an exposed implementation yet.