Fixes #2806
Fixes #3197
Fixes #3138

Inherited privacy doesn't work yet. This probably requires a snapshot since
it won't be backwards compatible. Additionally, two errors are printed instead
of one. For this reason the test is XFAIL'd.

rustc: Remove a few allocations from metadata. Shaves a few milliseconds off compilation of hello world.

this will require more temporaries, but is probably less magical.
also, it means that borrowck matches trans better, so fewer crashes.
bonus.

Finally, stop warning about implicit copies when we are actually borrowing.

Also, one test (vec-res-add) stopped failing due to #2587, and hence I
added an xfail-test.

Fixes #3217, #2977, #3067

This commit breaks the item-printing functionality. It will return in a faster
form.

Embarrassing.

There is also code for ~Trait and &Trait, but these are currently (incorrectly)
synonyms for "as @Trait" and "as &Trait".

Closes #3096