Almost all these functions already had #[inline]. These were missing.

std::format and core::write macros' docs linked to core::fmt for format string reference, even though only std::fmt has format string documentation and the link titles were std::fmt.

Co-authored-by: Mara Bos <m-ou.se@m-ou.se>

…eddyb

Add #[inline] to some functions in core::str.

Almost all str functions already had #[inline].

Fix doc links to std::fmt

`std::format` and `core::write` macros' docs linked to `core::fmt` for format string reference, even though only `std::fmt` has format string documentation (and the link titles were `std::fmt`)

Add note to process::arg[s] that args shouldn't be escaped or quoted

This came out of discussion on [forum](https://users.rust-lang.org/t/how-to-get-full-output-from-command/50626), where I recently asked a question and it turned out that the problem was redundant quotation:

```rust
 Command::new("rg")
        .arg("\"pattern\"") // this will look for "pattern" with quotes included
```

This is something that has bitten me few times already (in multiple languages actually), so It'd be grateful to have it in the docs, even though it's not sctrictly Rust specific problem. Other users also agreed.

This can be really annoying to debug, because in many cases (inluding mine), quotes can be legal part of the argument, so the command doesn't fail, it just behaves unexpectedly. Not everybody (including me) knows that quotes around arguments are part of the shell and not part of the called program. Coincidentally, somoene had the same problem [yesterday](https://www.reddit.com/r/rust/comments/jkxelc/going_crazy_over_running_a_curl_process_from_rust/) on reddit.

I am not a native speaker, so I welcome any corrections or better formulation, I don't expect this to be merged as is. I was also reminded that this is platform/shell specific behaviour, but I didn't find a good way to formulate that briefly, any ideas welcome.

 It's also my first PR here, so I am not sure I did everything correctly, I did this just from Github UI.

…=m-ou-se

fix various aliasing issues in the standard library

This fixes various cases where the standard library either used raw pointers after they were already invalidated by using the original reference again, or created raw pointers for one element of a slice and used it to access neighboring elements.

…asper

expand: Tweak a comment in implementation of `macro_rules`

The answer to the removed FIXME is that we don't apply mark to the span `sp` just because that span is no longer used. We could apply it, but that would just be unnecessary extra work.

The comments in code tell why the span is unused, it's a span of `$var` literally, which is lost for `tt` variables because their tokens are outputted directly, but kept for other variables which are outputted as [groups](https://doc.rust-lang.org/nightly/proc_macro/struct.Group.html) and `sp` is kept as the group's span.

Closes rust-lang#2887

Inline Default::default() for atomics

Functions like `AtomicUsize::default()` are not cross-crate inlineable before this PR ([see assembly output here](https://play.rust-lang.org/?version=stable&mode=release&edition=2018&gist=e353321766418f759c69fb141d3732f8)), which can lead to unexpected performance issues when initializing a large array using this function, e.g. as seen [here](https://github.com/spacejam/sled/blob/d513996a85875be8c813fd0e30a548b89682289a/src/histogram.rs#L53) which should turn into a simple loop writing zeroes but doesn't.

r? @m-ou-se