repr: write the mutability qualifier for slices
repr: update for removal of const
auto merge of #9066 : thestinger/rust/repr, r=alexcrichton
rename `std::iterator` to `std::iter`

The trait will keep the `Iterator` naming, but a more concise module
name makes using the free functions less verbose. The module will define
iterables in addition to iterators, as it deals with iteration in
general.
auto merge of #9065 : thestinger/rust/iter, r=alexcrichton

The trait will keep the `Iterator` naming, but a more concise module
name makes using the free functions less verbose. The module will define
iterables in addition to iterators, as it deals with iteration in
general.
Remove hacks around issues in local_data

These compiler bugs have since been fixed (one less layer of indirection)
auto merge of #9073 : alexcrichton/rust/remove-local-data-hax, r=huonw

These compiler bugs have since been fixed (one less layer of indirection)
Some work on std::ascii: Marked unsafe function unsafe, added moving implementations