Reapplied the changes from https://github.com/freebroccolo/rust/commit/dc64b731d7f66c2b43d5e5e8c721be7bd3b59540
to a clean branch of master

Add a new method `CommandExt::session_leader(&mut self, on: bool)` to create a new session (cf. `setsid(2)`) for the child process. This means that the child is the leader of a new process group. The parent process remains the child reaper of the new process.

This is not enough to create a daemon process. The *init* process should be the child reaper of a daemon. This can be achieved if the parent process exit. Moreover, a daemon should not have a controlling terminal. To acheive this, a session leader (the child) must spawn another process (the daemon) in the same session.

cc rust-lang/rfcs#941
cc #17176

Some small changes to (hopefully) make search more useful:

* Less strict filtering, e.g:
    * searching for "fn: foo" now matches methods and trait functions as well.
    * searching for types also matches primitive types.
    * searching for const will also match associated constants (but there aren't any in std yet)
* Changed searching for types to use the actual keyword "type" instead of the strange C-like "typedef".
* Added const and macro to allowed keywords.

For #27501  

r? @steveklabnik

- Successful merges: #27397, #27398, #27460, #27470, #27491, #27498, #27502
- Failed merges: 

this grammar isn't correct

this should also get backported to beta

/cc @brson 

r? @Gankro 

For https://github.com/rust-lang/rust/issues/24407

  - Fix #26968 by noting the difference between ".." and "_" more explicitly

  - Change one of the examples to show the match-all behaviour of ".."

  - Merge "Ignoring variants" and "Ignoring bindings" sections into the latter

r? @steveklabnik

Clarifications for those new to Rust and Cargo:
* It's a good idea to get rid of the original `main.exe` in project root
* Slight clarification on the use of `main.rs` vs `lib.rs`
* Clarify that the TOML file needs to be in project root

Fixes #27467.

Closes #27412 

r? @brson

This test case has been removed a while ago because it allegedly was broken. But I don't think it is (at least I couldn't reproduce any failure on Linux). Let's give it another chance `:)`

Fixes #27467.

After #26694, the overloaded operator and "impl not known at method lookup time" cases started triggering the lint.
I've also added checks for overloaded autoderef and method calls via paths (i.e. `T::method()`).
All new 8 test cases did not trigger the lint before #26694.
r? @huonw

After this change, the only remaining symbol we are pulling from libgcc on Win64 is `__chkstk_ms` - the stack probing routine.

Fixes #25022

This adapts the deriving mechanism to not repeat bounds for the same type parameter. To give an example: for the following code:

```rust
#[derive(Clone)]
pub struct FlatMap<I, U: IntoIterator, F> {
    iter: I,
    f: F,
    frontiter: Option<U::IntoIter>,
    backiter: Option<U::IntoIter>,
}
```
the latest nightly generates the following impl signature:

```rust
impl <I: ::std::clone::Clone,
      U: ::std::clone::Clone + IntoIterator,
      F: ::std::clone::Clone>
::std::clone::Clone for FlatMap<I, U, F> where
    I: ::std::clone::Clone,
    F: ::std::clone::Clone,
    U::IntoIter: ::std::clone::Clone,
    U::IntoIter: ::std::clone::Clone
```

With these changes, the signature changes to this:
```rust
impl <I, U: IntoIterator, F> ::std::clone::Clone for FlatMap<I, U, F> where
    I: ::std::clone::Clone,
    F: ::std::clone::Clone,
    U::IntoIter: ::std::clone::Clone
```
(Nothing in the body of the impl changes)
Note that the second impl is more permissive, as it doesn't have a `Clone` bound on `U` at all. There was a compile-fail test that failed due to this. I don't understand why we would want the old behaviour (and nobody on IRC could tell me either), so please tell me if there is a good reason that I missed.

this grammar isn't correct

Inspired by https://github.com/rust-lang/rust/issues/27484

- Successful merges: #27464, #27473
- Failed merges: 

This removes some of the more casual language.

The only outright goofiness I couldn't bear to remove is "these modules are the bedrock upon which all of Rust is forged, and they have mighty names like `std::slice` and `std::cmp`", which I believe the greatest sentence I have ever created.

Because Markdown.