libs: stabilize iter module

This is an initial pass at stabilizing the `iter` module. The module is
fairly large, but is also pretty polished, so most of the stabilization
leaves things as they are.

Some changes:

* Due to the new object safety rules, various traits needs to be split
  into object-safe traits and extension traits. This includes `Iterator`
  itself. While splitting up the traits adds some complexity, it will
  also increase flexbility: once we have automatic impls of `Trait` for
  trait objects over `Trait`, then things like the iterator adapters
  will all work with trait objects.

* Iterator adapters that use up the entire iterator now take it by
  value, which makes the semantics more clear and helps catch bugs. Due
  to the splitting of Iterator, this does not affect trait objects. If
  the underlying iterator is still desired for some reason, `by_ref` can
  be used. (Note: this change had no fallout in the Rust distro except
  for the useless mut lint.)

* In general, extension traits new and old are following an [in-progress
  convention](https://github.com/rust-lang/rfcs/pull/445). As such, they
  are marked `unstable`.

* As usual, anything involving closures is `unstable` pending unboxed
  closures.

* A few of the more esoteric/underdeveloped iterator forms (like
  `RandomAccessIterator` and `MutableDoubleEndedIterator`, along with
  various unfolds) are left experimental for now.

* The `order` submodule is left `experimental` because it will hopefully
  be replaced by generalized comparison traits.

* "Leaf" iterators (like `Repeat` and `Counter`) are uniformly
  constructed by free fns at the module level. That's because the types
  are not otherwise of any significance (if we had `impl Trait`, you
  wouldn't want to define a type at all).

Closes #17701

Due to renamings and splitting of traits, this is a:

[breaking-change]
Fallout from stabilization
Add -Z print-sysroot commandline option to rustc.
debuginfo: Add script that allows to conveniently start LLDB in "rust-mode"
debuginfo: Fix LLDB pretty printer for enum variants with zero fields.
auto merge of #19176 : aturon/rust/stab-iter, r=alexcrichton

This is an initial pass at stabilizing the `iter` module. The module is
fairly large, but is also pretty polished, so most of the stabilization
leaves things as they are.

Some changes:

* Due to the new object safety rules, various traits needs to be split
  into object-safe traits and extension traits. This includes `Iterator`
  itself. While splitting up the traits adds some complexity, it will
  also increase flexbility: once we have automatic impls of `Trait` for
  trait objects over `Trait`, then things like the iterator adapters
  will all work with trait objects.

* Iterator adapters that use up the entire iterator now take it by
  value, which makes the semantics more clear and helps catch bugs. Due
  to the splitting of Iterator, this does not affect trait objects. If
  the underlying iterator is still desired for some reason, `by_ref` can
  be used. (Note: this change had no fallout in the Rust distro except
  for the useless mut lint.)

* In general, extension traits new and old are following an [in-progress
  convention](rust-lang/rfcs#445). As such, they
  are marked `unstable`.

* As usual, anything involving closures is `unstable` pending unboxed
  closures.

* A few of the more esoteric/underdeveloped iterator forms (like
  `RandomAccessIterator` and `MutableDoubleEndedIterator`, along with
  various unfolds) are left experimental for now.

* The `order` submodule is left `experimental` because it will hopefully
  be replaced by generalized comparison traits.

* "Leaf" iterators (like `Repeat` and `Counter`) are uniformly
  constructed by free fns at the module level. That's because the types
  are not otherwise of any significance (if we had `impl Trait`, you
  wouldn't want to define a type at all).

Closes #17701

Due to renamings and splitting of traits, this is a:

[breaking-change]
auto merge of #19144 : michaelwoerister/rust/lldb-scripts, r=alexcrichton

This PR adds the `rust-lldb` script (feel free to bikeshed about the name).
The script will start LLDB and, before doing anything else, load [LLDB type summaries](http://lldb.llvm.org/varformats.html) that will make LLDB print values with Rust syntax. Just use the script like you would normally use LLDB:

```
rust-lldb executable-to-debug --and-any-other-commandline --args 
```
The script will just add one additional commandline argument to the LLDB invocation and pass along the rest of the arguments to LLDB after that.

Given the following program...
```rust
fn main() {
	let x = Some(1u);
	let y = [0, 1, 2i];
	let z = (x, y);

	println!("{} {} {}", x, y, z);
}
```
...*without* the 'LLDB type summaries', values will be printed something like this...
```
(lldb) p x
(core::option::Option<uint>) $3 = {
   = (RUST$ENUM$DISR = Some)
   = (RUST$ENUM$DISR = Some, 1)
}
(lldb) p y
(long [3]) $4 = ([0] = 0, [1] = 1, [2] = 2)
(lldb) p z
((core::option::Option<uint>, [int, ..3])) $5 = {
   = {
     = (RUST$ENUM$DISR = Some)
     = (RUST$ENUM$DISR = Some, 1)
  }
   = ([0] = 0, [1] = 1, [2] = 2)
}
```
...*with* the 'LLDB type summaries', values will be printed like this:
```
(lldb) p x
(core::option::Option<uint>) $0 = Some(1)
(lldb) p y
(long [3]) $1 = [0, 1, 2]
(lldb) p z
((core::option::Option<uint>, [int, ..3])) $2 = (Some(1), [0, 1, 2])
```

The 'LLDB type summaries' used by the script have been in use for a while in the LLDB autotests but I still consider them to be of alpha-version quality. If you see anything weird when you use them, feel free to file an issue.

The script will use whatever Rust "installation" is in PATH, so whichever `rustc` will be called if you type `rustc` into the console, this is the one that the script will ask for the LLDB extension module location. The build system will take care of putting the script and LLDB python module in the right places, whether you want to use the stage1 or stage2 compiler or the one coming with `make install` / `rustup.sh`.

Since I don't have much experience with the build system, Makefiles and shell scripts, please look these changes over carefully.
rollup merge of #19224: frewsxcv/unprefix-json-types

Addressing the issues brought up in [this thread](https://github.com/rust-lang/rust/pull/19114#discussion_r20614461)

This pull request:

* Unpublicizes reexports
* Renames type aliases:
 * `json::JsonArray` ☞ `json::Array`
 * `json::JsonObject` ☞ `json::Object`
rollup merge of #19231: Gankro/ringbuf-into-iter

r? @huonw @csherratt
rollup merge of #19266: aochagavia/const

With this PR, the following code works:

```
#![feature(tuple_indexing)]
struct MyStruct { field1: uint }

const S: MyStruct = MyStruct { field1: 42u };
const T: (uint,) = (42u,);

struct ConstCheck {
    array1: [int, ..S.field1],
    array2: [int, ..T.0],
}
```

Closes https://github.com/rust-lang/rust/issues/19244
Related https://github.com/rust-lang/rust/issues/19265
rollup merge of #19272: tomjakubowski/rustdoc-sized

Both `trait Foo for Sized?` and `<Sized? T>` are handled correctly.

Fix #18515
rollup merge of #19273: ogham/rename-file-types

All of the enum components had a redundant 'Type' specifier: TypeSymlink, TypeDirectory, TypeFile. This change removes them, replacing them with a namespace: FileType::Symlink, FileType::Directory, and FileType::RegularFile.

RegularFile is used instead of just File, as File by itself could be mistakenly thought of as referring to the struct.

Part of #19253.
rollup merge of #19282: steveklabnik/remove_grammar

I stumbled across this today, and it's not really working. It's been around for a very, very long time, and seems to be based on stuff we don't even have anymore.

I asked in `#rust-internals`, and @cmr said we should just kill it, so here I am. :) I don't think that anything else uses Java, but maybe I missed something.

And if this _isn't_ what we want, I'm fine with closing too. Just some housekeeping.
rollup merge of #19287: alexcrichton/issue-19272

At the same time remove the `pub use` of the variants in favor of accessing
through the enum type itself. This is a breaking change as the `Found` and
`NotFound` variants must now be imported through `BinarySearchResult` instead of
just `std::slice`.

[breaking-change]
Closes #19271
rollup merge of #19288: steveklabnik/doc_style_cleanup

This is considered good convention.

This is about half of them in total, I just don't want an impossible to land patch. :smile:
rollup merge of #19296: csouth3/trieset-union

TrieSet doesn't yet have union, intersection, difference, and symmetric difference functions implemented.  Luckily, TrieSet is largely similar to TreeSet, so I was able to reference the implementations of these functions in the latter, and adapt them as necessary to make them work for TrieSet.

One thing that I thought was interesting is that the Iterator yielded by `iter()` for TrieSet iterates over the set's values directly rather than references to the values (whereas I think in most cases I see the Iterator given by `iter()` iterating over immutable references), so for consistency within TrieSet's interface, all of these Iterators also iterate over the values directly.  Let me know if all of these should be instead iterating over references.
rollup merge of #19298: nikomatsakis/unboxed-closure-parse-the-plus

Implements RFC 438.

Fixes #19092.

This is a [breaking-change]: change types like `&Foo+Send` or `&'a mut Foo+'a` to `&(Foo+Send)` and `&'a mut (Foo+'a)`, respectively.

r? @brson
rollup merge of #19299: nikomatsakis/stop-indenting-test-output

This fixes a long-time irritant of mine. Inserting tabs causes M-x next-error to not work in emacs and seems to serve relatively little purpose in improving overall readability.

r? @brson
rollup merge of #19300: killercup/patch-1

Just saw this when looking at #19297 and couldn't find an issue/PR dealing with this. #18773 seems to have missed this file.

Compiler output is generated [here](https://github.com/rust-lang/rust/blob/770378a313a573776b16237a46b75bafa49072c1/src/librustc_trans/driver/mod.rs#L466).

cc @steveklabnik
rollup merge of #19301: Gankro/take-fix

Was taking the value out correctly, but then not doing anything to actually fix the table. derp.