Add auto traits and clone trait migrations for RFC2229 This PR - renames the existent RFC2229 migration `disjoint_capture_drop_reorder` to `disjoint_capture_migration` - add additional migrations for auto traits and clone trait Closes rust-lang/project-rfc-2229#29 Closes rust-lang/project-rfc-2229#28 r? `@nikomatsakis`
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.