Before:
```
thread 'main' panicked at 'Unable to build RLS', dist.rs:42:9
```

After:
```
thread 'main' panicked at 'Unable to build submodule tool RLS (use `missing-tools = true` to ignore this failure)
note: not all tools are available on all nightlies
help: see https://forge.rust-lang.org/infra/toolstate.html for more information', dist.rs:43:9
```

This is first step in implementing RFC 3216.
- Parse `for<'a>` before closures in ast
  - Error in lowering
- Add `closure_lifetime_binder` feature

This helps bring `hir::Expr` size down, `Closure` was the biggest
variant, especially after `for<>` additions.

Line spans were incorrect if the first line of an asm statement was an
empty string.

This only stabilizes the base types, not the non-zero variants, since
those have their own separate tracking issue and have not gone through
FCP to stabilize.

Always create elided lifetime parameters for functions

Anonymous and elided lifetimes in functions are sometimes (async fns) --and sometimes not (regular fns)-- desugared to implicit generic parameters.

This difference of treatment makes it some downstream analyses more complicated to handle.  This step is a pre-requisite to perform lifetime elision resolution on AST.

There is currently an inconsistency in the treatment of argument-position impl-trait for functions and async fns:
```rust
trait Foo<'a> {}
fn foo(t: impl Foo<'_>) {} //~ ERROR missing lifetime specifier
async fn async_foo(t: impl Foo<'_>) {} //~ OK
fn bar(t: impl Iterator<Item = &'_ u8>) {} //~ ERROR missing lifetime specifier
async fn async_bar(t: impl Iterator<Item = &'_ u8>) {} //~ OK
```

The current implementation reports "missing lifetime specifier" on `foo`, but **accepts it** in `async_foo`.
This PR **proposes to accept** the anonymous lifetime in both cases as an extra generic lifetime parameter.
This change would be insta-stable, so let's ping t-lang.
Anonymous lifetimes in GAT bindings keep being forbidden:
```rust
fn foo(t: impl Foo<Assoc<'_> = Bar<'_>>) {}
                         ^^        ^^
                       forbidden   ok
```
I started a discussion here: https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/Anonymous.20lifetimes.20in.20universal.20impl-trait/near/284968606

r? `@petrochenkov`

…r=Mark-Simulacrum

Stabilize `core::ffi:c_*` and rexport in `std::ffi`

This only stabilizes the base types, not the non-zero variants, since
those have their own separate tracking issue and have not gone through
FCP to stabilize.

…llot

Implement `for<>` lifetime binder for closures

This PR implements RFC 3216 ([TI](rust-lang#97362)) and allows code like the following:

```rust
let _f = for<'a, 'b> |a: &'a A, b: &'b B| -> &'b C { b.c(a) };
//       ^^^^^^^^^^^--- new!
```

cc `@Aaron1011` `@cjgillot`

…acrum

Give a better error when `x dist` fails for an optional tool

Before:
```
thread 'main' panicked at 'Unable to build RLS', dist.rs:42:9
```

After:
```
thread 'main' panicked at 'Unable to build submodule tool RLS (use `missing-tools = true` to ignore this failure)
note: not all tools are available on all nightlies
help: see https://forge.rust-lang.org/infra/toolstate.html for more information', dist.rs:43:9
```

Closes rust-lang#85683 by explaining better why the error is expected.

Fix spans for asm diagnostics

Line spans were incorrect if the first line of an asm statement was an
empty string.