Allow non-Sized types in OffsetArc

[jplatte]

No description provided.

[Manishearth]

For future PRs please don't move APIs around, it makes it harder to review.

[jplatte]

I only moved from implicitly-T: Sized impl blocks to T: ?Sized impl blocks. Though I'm happy to redo this, e.g. by merging the impl blocks into one with T: ?Sized + T: Sized bounds on the relevant functions.

[Manishearth]

@jplatte No, your PR also moved some functions around in the file, please look at the diff. Perhaps you have some automatic tooling involved that ran without you realizing.

[jplatte]

No, I made all those changes myself and they did involve moving functions between different impl blocks. I already re-reviewed after your first comment. Which off the two changed files did you mean?

[Manishearth]

Ah, I see what happened. That makes sense, things were moved between impl blocks.