rust.md: Explicitly point out how special `'static` is.

Drive-by: fix description of `&content` to point out that `&'f type`
is (as of today) only for type expressions.
librustc: Record unique immutable borrows in the restrictions table.

This fixes borrow checking for closures. Code like this will break:

    struct Foo {
        x: int,
    }

    pub fn main() {
        let mut this = &mut Foo {
            x: 1,
        };
        let r = || {
            let p = &this.x;
            &mut this.x;
        };
        r()
    }

Change this code to not take multiple mutable references to the same value. For
example:

    struct Foo {
        x: int,
    }

    pub fn main() {
        let mut this = &mut Foo {
            x: 1,
        };
        let r = || {
            &mut this.x;
        };
        r()
    }

Closes #16361.

[breaking-change]
librustc: Use the correct categorized mutable type for the pattern in
`for` loop heads.

This breaks code like:

    let x = Some(box 1i);
        for &a in x.iter() {
    }

Change this code to obey the borrow checking rules. For example:

    let x = Some(box 1i);
        for &ref a in x.iter() {
    }

Closes #16205.

[breaking-change]
Revert "don't translate items when monomorphizing foreign-ABI functions"

This reverts commit 0c158b4fbfcec7d6f18859661047dff2109fdfe4.
Revert "avoid redundant translation of items during monomorphization"

This reverts commit f97f65f7b70e455c1c3e72e620120c9f1a96d89a.

Conflicts:
	src/librustc/middle/trans/base.rs
	src/librustc/middle/trans/foreign.rs
	src/librustc/middle/trans/monomorphize.rs
more consistent handling of inner items
auto merge of #16452 : epdtry/rust/unreachable-item-ice, r=pcwalton

This code produces an ICE:

```rust
#![crate_type = "rlib"]
fn main() {
    if true { return }
    // remaining code is unreachable
    match () {
        () => { static MAGIC: uint = 0; }
    }
}
```
([playpen](http://is.gd/iwOISB))

The error is "encode_symbol: id not found 18", where 18 is the `NodeId` of the declaration of `MAGIC`.  The problem is that `rustc` tries to emit metadata for `MAGIC`, but some of the information is missing because `MAGIC` never gets translated by `trans_item` - the entire body of the `match` gets skipped because the `match` itself is unreachable.

This branch simplifies the handling of inner items by always processing them using the `trans_item` visitor, instead of sometimes using the visitor and sometimes waiting until `trans_stmt` encounters the item.  This fixes the ICE by making the translation of the item no longer depend on the declaration being reachable code.  This branch also reverts #16059 and #16359, since the new change to item translation fixes the same problems as those but is simpler.
libnative: process spawning should not close inherited file descriptors

* The caller should be responsible for cleaning up file descriptors
* If a caller safely creates a file descriptor (via
  native::io::file::open) the returned structure (FileDesc) will try to
  clean up the file, failing in the process and writing error messages
  to the screen.
* This should not happen as the caller has no public interface for
  telling the FileDesc structure to NOT free the underlying fd.
* Alternatively, if another file is opened under the same fd held by
  the FileDesc structure returned by native::io::file::open, it will
  close the wrong file upon destruction.
auto merge of #16458 : pcwalton/rust/borrowck-for-moves, r=nikomatsakis

`for` loop heads.

This breaks code like:

    let x = Some(box 1i);
    for &a in x.iter() {
    }

Change this code to obey the borrow checking rules. For example:

    let x = Some(box 1i);
    for &ref a in x.iter() {
    }

Closes #16205.

[breaking-change]

r? @nikomatsakis
auto merge of #16460 : pcwalton/rust/borrowck-closure-issue, r=nikomatsakis

This fixes borrow checking for closures. Code like this will break:

    struct Foo {
        x: int,
    }

    pub fn main() {
        let mut this = &mut Foo {
            x: 1,
        };
        let r = || {
            let p = &this.x;
            &mut this.x;
        };
        r()
    }

Change this code to not take multiple mutable references to the same value. For
example:

    struct Foo {
        x: int,
    }

    pub fn main() {
        let mut this = &mut Foo {
            x: 1,
        };
        let r = || {
            &mut this.x;
        };
        r()
    }

Closes #16361.

[breaking-change]

r? @nikomatsakis
auto merge of #16421 : ipetkov/rust/cmd-fd-fix-retry, r=alexcrichton

Retry pull requesting of https://github.com/rust-lang/rust/pull/16407 after accidentally messing up rebasing of branches and making bors think the PR was merged
auto merge of #16381 : pnkfelix/rust/fsk-rust.md-fixes, r=alexcrichton

rust.md: Explicitly point out how special `'static` is.

Drive-by: fix description of `&content` to point out that `&'f type` is (as of today) only for type expressions.