If not, the error `does not have these features: foo` confused. 
r? @steveklabnik

…tStruct {}`).

- minor pronoun fix We -> You
- PATH troubleshooting
- dir output is vertical (but did not include timestamps)
- executables not in %PATH% require .\

When resolving a hostname, pass a hints struct where ai_socktype is
set to SOCK_STREAM in order to eliminate repeated results for each
protocol family.

Revise wording in Rc documentation.

The term "thread-local" has a widely accepted meaning which is not
the meaning it's used for here.

…, r=steveklabnik

Add doc examples for `io::Error::from_raw_os_error`.

None

…eveklabnik

Fix `std::path::Path::file_name()` doc

Fixes rust-lang#34632

r? @steveklabnik

…r, r=steveklabnik

Improve DoubleEndedIterator examples

Fixes rust-lang#34065.

r? @steveklabnik

…uct_checks, r=nrc

parser: Remove outdated checks for empty braced struct expressions (`S {}`)

This is a pure refactoring.
r? @nrc

enhancewindows documentation in getting-started

- minor pronoun fix We -> You
- PATH troubleshooting
- dir output is vertical (but did not include timestamps)
- executables not in %PATH% require .\

r? @steveklabnik

Use hints with getaddrinfo() in std::net::lookup_host()

As noted in rust-lang#24250, `std::net::lookup_host()` repeats each IPv[46] address in the result set. The number of repetitions is OS-dependent; e.g., Linux and FreeBSD give three copies, OpenBSD gives two. Filtering the duplicates can be done by the user if `lookup_host()` is used explicitly, but not with functions like `TcpStream::connect()`. What happens with the latter is that any unsuccessful connection attempt will be repeated as many times as there are duplicates of the address.

The program:

```rust
use std::net::TcpStream;

fn main() {
    let _stream = TcpStream::connect("localhost:4444").unwrap();
}
```

results in the following capture:

[capture-before.txt](https://github.com/rust-lang/rust/files/352004/capture-before.txt)

assuming that "localhost" resolves both to ::1 and 127.0.0.1, and that the listening program opens just an IPv4 socket (e.g., `nc -l 127.0.0.1 4444`.) The reason for this behavior is explained in [this comment](rust-lang#24250 (comment)): `getaddrinfo()` is not constrained.

Various OSS projects (I checked out Postfix, OpenLDAP, Apache HTTPD and BIND) which use `getaddrinfo()` generally constrain the result set by using a non-NULL `hints` parameter and setting at least `ai_socktype` to `SOCK_STREAM`. `SOCK_DGRAM` would also work. Other parameters are unnecessary for pure name resolution.

The patch in this PR initializes a `hints` struct and passes it to `getaddrinfo()`, which eliminates the duplicates. The same test program as above with this change produces:

[capture-after.txt](https://github.com/rust-lang/rust/files/352042/capture-after.txt)

All `libstd` tests pass with this patch.