Very minor fix: in `std::net::Ipv6Addr::new`, the documentation had an incomplete representation of the resulting address, missing the last two groups.

The alignment field is actually a "pointer sized" type instead of always i64,
requiring that the size of the padding field is also calculated slightly
differently.

Closes rust-lang#23425

This commit clarifies some of the unstable features in the `str` module by
moving them out of the blanket `core` and `collections` features.

The following methods were moved to the `str_char` feature which generally
encompasses decoding specific characters from a `str` and dealing with the
result. It is unclear if any of these methods need to be stabilized for 1.0 and
the most conservative route for now is to continue providing them but to leave
them as unstable under a more specific name.

* `is_char_boundary`
* `char_at`
* `char_range_at`
* `char_at_reverse`
* `char_range_at_reverse`
* `slice_shift_char`

The following methods were moved into the generic `unicode` feature as they are
specifically enabled by the `unicode` crate itself.

* `nfd_chars`
* `nfkd_chars`
* `nfc_chars`
* `graphemes`
* `grapheme_indices`
* `width`

Closes rust-lang#23451.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

 This commit clarifies some of the unstable features in the `str` module by
moving them out of the blanket `core` and `collections` features.

The following methods were moved to the `str_char` feature which generally
encompasses decoding specific characters from a `str` and dealing with the
result. It is unclear if any of these methods need to be stabilized for 1.0 and
the most conservative route for now is to continue providing them but to leave
them as unstable under a more specific name.

* `is_char_boundary`
* `char_at`
* `char_range_at`
* `char_at_reverse`
* `char_range_at_reverse`
* `slice_shift_char`

The following methods were moved into the generic `unicode` feature as they are
specifically enabled by the `unicode` crate itself.

* `nfd_chars`
* `nfkd_chars`
* `nfc_chars`
* `graphemes`
* `grapheme_indices`
* `width`

…=sanxiyn

 Closes rust-lang#23451.

…r=Manishearth

 Since module `std::sync::mpsc` is stable now, fix the deprecated link `comm` with `sync::mpsc`.

…x, r=steveklabnik

 Very minor fix: in `std::net::Ipv6Addr::new`, the documentation had an incomplete representation of the resulting address, missing the last two groups.

…r=brson

 The alignment field is actually a \"pointer sized\" type instead of always i64,
requiring that the size of the padding field is also calculated slightly
differently.

Closes rust-lang#23425

 I often have to run `ast-json` or look into the pretty-printer source to figure out what the fields of an AST enum mean. I've tried to document most of what I know (and some semi-obvious stuff).

r? @steveklabnik

f? @eddyb