`@@Trait` will not be adjusted properly if the method receiver has explicit self

[pcwalton]

We currently ignore adjustments for explicit self-ified method receivers in objects, which is wrong.

[catamorphism]

Bumping to 0.7

[catamorphism]

Seems non-critical for 0.7. Nominating for milestone 3, feature-complete.

[nikomatsakis]

Dup of #5762