Wire up cprng syscall as provider for rand::os::OsRng on Fuchsia.

This patch adds support for the aarch64-unknown-fuchsia target. Also
updates src/liblibc submodule to include required libc change.

This avoids 800,000 heap allocations when compiling html5ever.

This avoids 800,000 heap allocations when compiling html5ever. It
requires tweaking `SmallVector` a little.

This avoids 800,000 allocations when compiling html5ever.

Implement .fold() specifically for .map() and .cloned() so that any
inner fold improvements are available through map and cloned.

Chain can do something interesting here where it passes on the fold
into its inner iterators.

The lets the underlying iterator's custom fold() be used, and skips the
regular chain logic in next.

save_analysis: Dump data only if get_path_data doesn't fail to resolve a path.

Solves rust-lang#37126

Dump data only if `get_path_data` doesn't fail to resolve a path.
`get_path_data` returns `None` when it have to deals with `Def::Err`, which is used as placeholder for a failed resolution.

Tell me if this is good enough, maybe I have to add some tests ?

r? @nrc

Implement Iterator::fold for .chain(), .cloned(), .map() and the VecDeque iterators.

Chain can do something interesting here where it passes on the fold
into its inner iterators.

The lets the underlying iterator's custom fold() be used, and skips the
regular chain logic in next.

Also implement .fold() specifically for .map() and .cloned() so that any
inner fold improvements are available through map and cloned.

The same way, a VecDeque iterator fold can be turned into two slice folds.

These changes lend the power of the slice iterator's loop codegen to
VecDeque, and to chains and flat maps of slice iterators, and so on.
It's an improvement for .sum() and .product(), and other uses of fold.

run rustfmt on librustc_metadata folder

Support `use *;` and `use ::*;`.

Fixes rust-lang#31484.
r? @nrc

Avoid more allocations when compiling html5ever

These three commits reduce the number of allocations performed when compiling html5ever from 13.2M to 10.8M, which speeds up compilation by about 2%.

r? @nrc

Prohibit patterns in trait methods without bodies

They are not properly type checked
```rust
trait Tr {
    fn f(&a: u8); // <- This compiles
}
```
, mostly rejected by the parser already and generally don't make much sense.
This PR is kind of a missing part of rust-lang#35015.

Needs crater run.
cc rust-lang#35078 (comment) rust-lang#35015 rust-lang/rfcs#1685 rust-lang#35203
r? @eddyb

…chton

Add support for kernel randomness for Fuchsia

Wire up cprng syscall as provider for rand::os::OsRng on Fuchsia.

…ichton

Support for aarch64 architecture on Fuchsia

This patch adds support for the aarch64-unknown-fuchsia target. Also
updates src/liblibc submodule to include required libc change.

…-ptr, r=eddyb

rustc_typeck: Allow reification from fn item to unsafe ptr

See rust-lang/rfcs#1762.

I've never contributed to the compiler internals before-- apologies if I'm not going about this the right way.

Broken links in Vec docs

Fixed some issues with quote/bracket nesting and made quoting more consistent.

r? @steveklabnik

…chton

Print out the error when HeapFree failures do occur

cc rust-lang#37395

I'd prefer to use `assert!` instead of `debug_assert!` if the cost is acceptable.

r? @alexcrichton