[PATCH v13 2/5] rust: support formatting of foreign types

[Andrew Lunn]

> OK, with all the splitting requested, this comes out to ~54 patches.
> I'll send the first bit (which can go in cycle 0) as v14.

FYI: Some subsystems have limits as to how many patches can be posted
at once. e.g. for netdev, don't send more than 15.

This is another rule about making it easier for reviewers. If i see 20
patches, i will defer reviewing them until later, when i have more
time. For a handful of patches, especially small obvious patches, i'm
more likely to look at them straight away.

	Andrew