Fix rust-lang#65635.

This code was added to avoid UB in LLVM 6 and earlier, but we no longer support those LLVM versions.
Since https://reviews.llvm.org/D47807 (released in LLVM 7), uitofp does exactly what we need.

Closes rust-lang#51872

PR rust-lang#66512 added the ability to set argv[0] on
Command. As a side effect, it changed the Debug output to print both the program and
argv[0], which in practice results in stuttery output ("echo echo foo").

This PR reverts the behaviour to the the old one, so that the command is only printed
once - unless arg0 has been set. In that case it emits "[command] arg0 arg1 ...".

config.rs has reached the 3000 line tidy limit, this commit moves
command line option definitions into a new file - options.rs,  and
leaves the rest of configuration infrastructure in config.rs.

…morse

Remove a const-if-hack in RawVec

r? @ecstatic-morse

cc @Centril

…=varkor

Use structured suggestion for disambiguating method calls

Fix rust-lang#65635.

…plett

Fix up Command Debug output when arg0 is specified.

PR rust-lang#66512 added the ability to set argv[0] on
Command. As a side effect, it changed the Debug output to print both the program and
argv[0], which in practice results in stuttery output (`"echo" "echo" "foo"`).

This PR reverts the behaviour to the the old one, so that the command is only printed
once - unless arg0 has been set. In that case it emits `"[command]" "arg0" "arg1" ...`.

…type-parameter, r=estebank

Indicate origin of where type parameter for uninferred types

Based on rust-lang#65951 (which is not merge yet), fixes rust-lang#67277.

This PR improves a little the diagnostic for code like:

```
 async fn foo() {
     bar().await;
}

 async fn bar<T>() -> () {}
```

by showing:
```
error[E0698]: type inside `async fn` body must be known in this context
 --> unresolved_type_param.rs:9:5
  |
9 |     bar().await;
  |     ^^^ cannot infer type for type parameter `T` declared on the function `bar`
  |
...
```
(The
```
declared on the function `bar`
```
part is new)

A small side note: `Vec` and `slice` seem to resist this change, because querying `item_name()` panics, and `get_opt_name()` returns `None`.

r? @estebank

…atthewjasper

Remove now-redundant range check on u128 -> f32 casts

This code was added to avoid UB in LLVM 6 and earlier, but we no longer support those LLVM versions.
Since https://reviews.llvm.org/D47807 (released in LLVM 7), uitofp does exactly what we need.

Closes rust-lang#51872

Move command line option definitions into a dedicated file

config.rs has reached the 3000 line tidy limit, this commit moves command line option definitions into a new file - options.rs,  and leaves the rest of configuration infrastructure in config.rs.

Remove `SOCK_CLOEXEC` dummy variable on platforms that don't use it.