Auto merge of #430 - asajeffrey:smup, r=jdm
Upgrade to SM 60
This is the mozjs_sys smup PR. Depends on https://github.com/servo/mozjs/pull/138.
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/rust-mozjs/430)
<!-- Reviewable:end -->
