Rollup of 10 pull requests

- Successful merges: #49443, #49445, #49446, #49463, #49464, #49466, #49468, #49473, #49484, #49486
- Failed merges:

Hide type declarations by default

I'm not very happy for the moment about the rendering but the bases are here:

<img width="610" alt="screen shot 2018-03-27 at 11 56 27" src="https://user-images.githubusercontent.com/3050060/37960492-0e045954-31b6-11e8-9cea-1ef8a3f980c4.png">

r? @QuietMisdreavus

correct a typo in RELEASES.md

Ignore stack-probes tests on powerpc/s390x too

We only support stack probes on x86 and x86_64.
Other arches are already ignored.

src/libcore/ptr.rs: Fix documentation for size of `Option<NonNull<T>>`

Seems more useful to say that it has the same size as `*mut T`.

Remove unnecessary use core::hash in liballoc/boxed.rs

It' only used for hash::Hasher, but Hasher is also imported.

Use f{32,64}::to_bits for is_zero test in vec::SpecFromElem

vec::SpecFromElem provides an optimization to use calloc to fill a Vec
when the element given to fill the Vec is represented by 0.

For floats, the test for that currently used is `x == 0. &&
x.is_sign_positive()`. When compiled in a standalone function, rustc
generates the following assembly:

```
  xorps xmm1, xmm1
  ucomisd xmm0, xmm1
  setnp al
  sete cl
  and cl, al
  movq rax, xmm0
  test rax, rax
  setns al
  and al, cl
  ret
```

A simpler test telling us whether the value is represented by 0, is
`x.to_bits() == 0`, which rustc compiles to:

```
  movq rax, xmm0
  test rax, rax
  sete al
  ret
```

Not that the test is hot in any way, but it also makes it clearer what
the intent in the rust code is.

rustbuild: Don't leak file handles when creating junctions on Windows

This fixes building the compiler docs because stage1-rustc\x86_64-pc-windows-msvc\doc is used twice which doesn't work if we still have a handle from the first time.

Don't mention unstable constructors in release notes

Explicitly mention `Option` in `?` error message.

Save users the time/effort of having to lookup what types implement
the `Try` trait.

Rename main theme into light theme

r? @QuietMisdreavus

Fix tooltip position

r? @QuietMisdreavus

rustc: Group linked libraries where needed

This commit fixes a longstanding issue with the compiler with circular
dependencies between libcore and libstd. The `core` crate requires at least one
symbol, the ability to unwind. The `std` crate is the crate which actually
defines this symbol, but the `std` crate also depends on the `core` crate.

This circular dependency is in general disallowed in Rust as crates cannot have
cycles amongst them. A special exception is made just for core/std, but this is
also unfortunately incompatible with how GNU linkers work. GNU linkers will
process undefined symbols in a left-to-right fashion, only actually linking an
rlib like libstd if there are any symbols used from it. This strategy is
incompatible with circular dependencies because if we otherwise don't use
symbols from libstd we don't discover that we needed it until we're later
processing libcore's symbols!

To fix this GNU linkers support the `--start-group` and `--end-group` options
which indicate "libraries between these markers may have circular dependencies
amongst them. The linker invocation has been updated to automatically pass these
arguments when we're invoking a GNU linker and automatically calculate where the
arguments need to go (around libstd and libcore)

Closes #18807
Closes #47074

This commit fixes a longstanding issue with the compiler with circular
dependencies between libcore and libstd. The `core` crate requires at least one
symbol, the ability to unwind. The `std` crate is the crate which actually
defines this symbol, but the `std` crate also depends on the `core` crate.

This circular dependency is in general disallowed in Rust as crates cannot have
cycles amongst them. A special exception is made just for core/std, but this is
also unfortunately incompatible with how GNU linkers work. GNU linkers will
process undefined symbols in a left-to-right fashion, only actually linking an
rlib like libstd if there are any symbols used from it. This strategy is
incompatible with circular dependencies because if we otherwise don't use
symbols from libstd we don't discover that we needed it until we're later
processing libcore's symbols!

To fix this GNU linkers support the `--start-group` and `--end-group` options
which indicate "libraries between these markers may have circular dependencies
amongst them. The linker invocation has been updated to automatically pass these
arguments when we're invoking a GNU linker and automatically calculate where the
arguments need to go (around libstd and libcore)

Closes #18807
Closes #47074

We only support stack probes on x86 and x86_64.
Other arches are already ignored.

Rename RangeArgument to RangeBounds, move it and Bound to libcore

As proposed in the tracking issue: https://github.com/rust-lang/rust/issues/30877

Changes to *stable* items:

* `core::ops::Bound` / `std::ops::Bound` is new
* `std::collections::Bound` is a deprecated reexport of it (does this actually cause a warning?)

Changes to *unstable* items

* `alloc::Bound` is gone
* `alloc::range::RangeArgument` is moved to `core::ops::RangeBounds` / `std::ops::RangeBounds`
* `alloc::range` is gone
* `std::collections::range::RangeArgument` is deprecated reexport, to be removed later
* `std::collections::range` is deprecated, to be removed later
* `impl RangeBounds<T> for Range{,From,To,Inclusive,ToInclusive}<&T>` are added

The idea of replacing this trait with a type to be used with `Into<_>` is left for future consideration / work.

(Fixes https://github.com/rust-lang-nursery/rust-clippy/issues/2552.)

These unstable items are deprecated:

* The `std::collections::range::RangeArgument` reexport
* The `std::collections::range` module.

The stable reexport `std::collections::Bound` is now deprecated.

Another deprecated reexport could be added in `alloc`,
but that crate is unstable.

Update Cargo

This includes https://github.com/rust-lang/cargo/pull/5255 which fixed regression in `cargo rustdoc` command.

If beta branches before this is merged, we'll need to backport as well

Seems more useful to say that it has the same size as `*mut T`.

This includes rust-lang/cargo#5255 which fixed regression in
`cargo rustdoc` command.

Remove universes from `ty::ParamEnv`

This change was never meant to land. #48407 takes an alternate approach. However, that PR is now blocked on some issues with canonicalization, and rebasing these reverts gets harder each time, so let's just get this bit out of the way now.

r? @nikomatsakis

Check for known but incorrect attributes

fixes #43988

- Change nested_visit_map so it will recursively check functions

- Add visit_stmt and visit_expr for impl Visitor for CheckAttrVisitor and check for incorrect
inline and repr attributes on staements and expressions

- Add regression test for issue #43988

It' only used for hash::Hasher, but Hasher is also imported.

Stabilize underscore lifetimes

r? @nikomatsakis

vec::SpecFromElem provides an optimization to use calloc to fill a Vec
when the element given to fill the Vec is represented by 0.

For floats, the test for that currently used is `x == 0. &&
x.is_sign_positive()`. When compiled in a standalone function, rustc
generates the following assembly:

```
  xorps xmm1, xmm1
  ucomisd xmm0, xmm1
  setnp al
  sete cl
  and cl, al
  movq rax, xmm0
  test rax, rax
  setns al
  and al, cl
  ret
```

A simpler test telling us whether the value is represented by 0, is
`x.to_bits() == 0`, which rustc compiles to:

```
  movq rax, xmm0
  test rax, rax
  sete al
  ret
```

Not that the test is hot in any way, but it also makes it clearer what
the intent in the rust code is.

Rollup of 12 pull requests

- Successful merges: #49243, #49329, #49364, #49400, #49405, #49427, #49428, #49429, #49439, #49442, #49444, #49452
- Failed merges:

This fixes building the compiler docs because stage1-rustc\x86_64-pc-windows-msvc\doc is used twice which
doesn't work if we still have a handle from the first time.

Remove hidden `foo` functions from doc examples; use `Termination` trait.

Fixes https://github.com/rust-lang/rust/issues/49233.

Easier to review with the white-space ignoring `?w=1` feature: https://github.com/rust-lang/rust/pull/49357/files?w=1

Clarify "length" wording in `Vec::with_capacity`.

Fixes https://github.com/rust-lang/rust/issues/49448.