std: Remove ThreadPerCore spawn mode. Unused
rustc compiler config for Vim.

Note that this is not actually *used* by default; it is a matter of
configuration still, because you might want to:

- Compile all .rs files with `rustc %` (where each can be built itself)

- Compile all .rs files with `rustc some-file.rs` (where you are editing
  part of a crate)

- Compile with a different tool, such as `make`. (In this case you might
  put a `~/.vim/after/compiler/rustc.vim` to match such cases, set
  makeprg and extend errorformat as appropriate. That should probably go
  in a different compiler mode, e.g. make-rustc.)

To try using it, `:compiler rustc`. Then, `:make` on a file you would
run `rustc` on will work its magic, invoking rustc. To automate this,
you could have something like `autocmd FileType rust compiler rustc` in
your Vim config.
extra: add tests for test::MetricMap, MetricDiff, ratchet.
extra: Add metrics functions to test.
compiletest: Add support for metrics and ratchet modes.
Add configure and make machinery to activate perf metrics and ratchets.
extra: reduce bench loop max time to 3s.
Rename Option swap_unwrap to take_unwrap. Fixes Issue#7764
Add project information to l10n templates.
test: new codegen tests, rename hello.
Provide more useful messages when tests are given -h or --help

Progress on #7824
Add a `get_mut` method for TLS

Simulates borrow checks for '@mut' boxes, or at least it's the same idea.
Sort lint attributes to print them in a more sane way

Closes #7818
tutorial: remove duplicate link references.

`pandoc` issues warnings.

```
pandoc: Duplicate link reference `[macros]' "source" (line 2151, column 1)
pandoc: Duplicate link reference `[tasks]' "source" (line 2150, column 1)
pandoc: Duplicate link reference `[wiki-start]' "source" (line 92, column 1)
```
auto merge of #7831 : ozten/rust/issues-7764-swap_unwarp-take-unwrap, r=pcwalton

Fixes Issue #7764

Running `make check` I do get a failure:

    test rt::io::extensions::test::push_bytes ... ok
    rustest rt::comm::test::oneshot_single_thread_send_port_close ... t: task failed at 'Unhandled condition:
     read_error: {kind: OtherIoError, desc: "Placeholder error. You shouldn\'t be seeing this", detail: None}',
     /Users/shout/Projects/rust/src/libstd/condition.rs:50
    /bin/sh: line 1: 35056 Abort trap: 6           x86_64-apple-darwin/stage2/test/stdtest-x86_64-apple-darwin --logfile
     tmp/check-stage2-T-x86_64-apple-darwin-H-x86_64-apple-darwin-std.log
    make: *** [tmp/check-stage2-T-x86_64-apple-darwin-H-x86_64-apple-darwin-std.ok] Error 134
Make all lang_items optional

Whenever a lang_item is required, some relevant message is displayed, often with
a span of what triggered the usage of the lang item
rustc: implement a `#[no_implicit_prelude]` attribute.

It disables the insertion of `use std::prelude::*;` into the top of
all the modules below the item on which it is placed (including that
item itself).
auto merge of #7828 : alexcrichton/rust/lang-opt, r=graydon

Whenever a lang_item is required, some relevant message is displayed, often with
a span of what triggered the usage of the lang item.

Now "hello word" is as small as:

```rust
#[no_std];

extern {
    fn puts(s: *u8);
}

extern "rust-intrinsic" {
    fn transmute<T, U>(t: T) -> U;
}

#[start]
fn main(_: int, _: **u8, _: *u8) -> int {
    unsafe {
        let (ptr, _): (*u8, uint) = transmute("Hello!");
        puts(ptr);
    }
    return 0;
}
```
Made ast::blk not use spanned<T> anymore.
tutorial: remove unused link references.