Register snapshots.
Transition to new `Hash`, removing IterBytes and std::to_bytes.
auto merge of #12492 : huonw/rust/snapshots, r=alexcrichton

Replaces IterBytes with the new Hash, removing all trace of the old implementation.
Removed rustdoc comments on pub mod statements in std::io's mod.rs. Tweaked wording of stdio's summary statement.
Move std::{trie, hashmap} to libcollections

These two containers are indeed collections, so their place is in
libcollections, not in libstd. There will always be a hash map as part of the
standard distribution of Rust, but by moving it out of the standard library it
makes libstd that much more portable to more platforms and environments.

This conveniently also removes the stuttering of 'std::hashmap::HashMap',
although 'collections::HashMap' is only one character shorter.
std: Move intrinsics to std::intrinsics.

Issue #1457
std: Move raw to std::raw

Issue #1457
std: Move unstable::stack to rt::stack
Removed rustdoc comments on  lines of std::io's mod.rs. Added rustdoc comments to test.rs and util.rs.
Transition to new `Hash`, removing IterBytes and std::to_bytes.
Move std::{trie, hashmap} to libcollections

These two containers are indeed collections, so their place is in
libcollections, not in libstd. There will always be a hash map as part of the
standard distribution of Rust, but by moving it out of the standard library it
makes libstd that much more portable to more platforms and environments.

This conveniently also removes the stuttering of 'std::hashmap::HashMap',
although 'collections::HashMap' is only one character shorter.
std: Move intrinsics to std::intrinsics.

Issue #1457
std: Move raw to std::raw

Issue #1457
std: Move unstable::stack to rt::stack