it -> Cargo

It wasn't clear if we needed to install Hello World or Cargo.
librustc: Don't ICE on binding same field multiple times in struct
pattern.
Allow external html in rustdoc for crates.

Updated documentation to reflect md->html.
Modularized external file loading.
auto merge of #15237 : zzmp/rust/feat/markdown-in-crate-documentation, r=huonw

This makes the `in-header`, `markdown-before-content`, and `markdown-after-content` options available to `rustdoc` when generating documentation for any crate.

Before, these options were only available when creating documentation *from* markdown. Now, they are available when generating documentation from source.

This also updates the `rustdoc -h` output to reflect these changes. It does not update the `man rustdoc` page, nor does it update the documentation in [the `rustdoc` manual](http://doc.rust-lang.org/rustdoc.html).
fix typo in readme
auto merge of #15262 : zecozephyr/rust/15620, r=luqmana

Fixes #15260
auto merge of #15259 : steveklabnik/rust/patch-3, r=alexcrichton

It wasn't clear if we needed to install Hello World or Cargo.
auto merge of #15267 : ruud-v-a/rust/patch-1, r=huonw

[This commit](https://github.com/rust-lang/rust/commit/25fe2cadb10db1a54cefbd1520708d4397874bc3#diff-04c6e90faac2675aa89e2176d2eec7d8R57) forgot to remove one line.
Fix distcheck

libcoretest wasn't being included which broke the verification of the
tarball.
auto merge of #15275 : sfackler/rust/distcheck, r=alexcrichton

libcoretest wasn't being included which broke the verification of the
tarball.
JSON cleanup

* Tried to make the code more idiomatic
* Renamed the `wr` field of the `Encoder` and `PrettyEncoder` structs to `writer`
* Replaced some `from_utf8` by `from_utf8_owned` to avoid unnecessary allocations
* Removed unnecessary `unsafe` code
Removed unnecessary Box
Add `encode` and `decode` shortcut functions

Now you can just use `json::encode` and `json::decode`, which is very
practical

**Deprecated `Encoder::str_encode` in favor of `json::encode`**

[breaking-change]
Implement FromStr for Json
Fix JSON documentation

Fixed some errors, removed some code examples and added usage of the
`encode` and `decode` functions.
Fix issues in libtest
Fix issue with tests
Fix issues in librustdoc
Implement ToJson for all tuples