[cfe-dev] noderef attribute

[Leonard Chan via cfe-dev]

> Any other attributes from Sparse you're interesting in adding, or just
> this one?

Not anything other immediate ones. We did have an idea of expanding
`address_space` into something that accepts names instead of just
numbers for representing address spaces in a more "verbose" way, but
that's down the road.

> If we have a function parameter that takes a noderef pointer, can we add
> the readnone attribute on the argument so that the optimizer knows that
> memory is not accessed through that pointer?

Will do. Initially I wanted to just replicate this part of sparse but
this makes sense to add.