Ok, for now I'll keep supporting `#[macro_use] #[no_link] extern crate foo` since it's used in the wild, but won't support importing macros from `#[no_link]
... crates with `use`.
Or maybe just support imports macros from `#[no_link] extern crate foo;` at the crate root
i.e. `#[no_link] extern crate foo;` defines a module `foo` with only macros, not types, values, or submodules (even if the submodules contain macros)
just support importing macros from `#[no_link] extern crate foo;` at *foo's* root