doc/guide-ffi: A few minor typo/language fixes

Signed-off-by: Anton Lofgren <alofgren@op5.com>
Add example for str replace() and MaybeOwned

  - for 3 implementations of into_maybe_owned()
  - is_slice()
  - is_owned()
Guide: match
Guide: looping
Guide: Standard input
librustc: Don't emit call for intrinsics instead just trans at callsite.
librustc: Remove old codepaths for creating intrinsic functions.
librustc: Update to reflect changes to how intrinsics are codegened.
Derive Clone for Command and StdioContainer
librustc: Translate input for transmute directly into dest.
libcore: Reexport a couple of widely-used low-level intrinsics to reduce
code bloat.

This didn't make a difference in any compile times that I saw, but it
fits what we're doing with `transmute` and seems prudent.
Use std::fmt::radix instead of to_str_radix.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Add range lint for float literals, fixing #10934
auto merge of #15566 : japaric/rust/command-clone, r=alexcrichton

Allows use cases like this one:

``` rust
use std::io::Command;

fn main() {
    let mut cmd = Command::new("ls");
    cmd.arg("-l");

    for &dir in ["a", "b", "c"].iter() {
        println!("{}", cmd.clone().arg(dir));
    }
}
```

Output:
```
ls '-l' 'a'
ls '-l' 'b'
ls '-l' 'c'
```
Without the `clone()`, you'll end up with:
```
ls '-l' 'a'
ls '-l' 'a' 'b'
ls '-l' 'a' 'b' 'c'
```

cc #15294
Mistake in AtomicBool spinlock example

The current example of a spinlock was not correct. The lock is actually acquired
when old == result. So we only need to deschedule when this is not the case.
typeck: check casts from pointers to floats, closes #15445
auto merge of #15563 : luqmana/rust/nif, r=pcwalton
Remove deprecated std::unstable module.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
auto merge of #15569 : pcwalton/rust/reexport-intrinsics, r=cmr

code bloat.

This didn't make a difference in any compile times that I saw, but it
fits what we're doing with `transmute` and seems prudent.

r? @alexcrichton
std: Add some implementation of common traits

- semver::Version is now Eq, Ord, and Hash
- Path is now PartialOrd and Ord