Relicense shootout-pidigits.rs

Everyone agreed.

Related to #14248, close #14718
Add examples of how to read from a channel with a timeout, refs #13862
auto merge of #14877 : Seldaek/rust/commdocs, r=alexcrichton

Finally what I promised to do in #13862 /cc @alexcrichton
std: Support consuming a Process without waiting

Forking off a child which survives the parent is often a useful task, and is
currently not possible because the Process type will invoke `wait()` in its
destructor in order to prevent leaking resources. This function adds a new safe
method, `forget`, which can be used to consume an instance of `Process` which
will then not call `wait` in the destructor.

This new method is clearly documented as a leak of resources, but it must be
forcibly opted in to.

Closes #14467
std: Improve pipe() functionality

* os::pipe() now returns IoResult<os::Pipe>
* os::pipe() is now unsafe because it does not arrange for deallocation of file
  descriptors
* os::Pipe fields are renamed from input to reader and out to write.
* PipeStream::pair() has been added. This is a safe method to get a pair of
  pipes.
* Dealing with pipes in native process bindings have been improved to be more
  robust in the face of failure and intermittent errors. This converts a few
  fail!() situations to Err situations.

Closes #9458
cc #13538
Closes #14724
[breaking-change]
auto merge of #14551 : alexcrichton/rust/issue-14467, r=kballard

Forking off a child which survives the parent is often a useful task, and is
currently not possible because the Process type will invoke `wait()` in its
destructor in order to prevent leaking resources. This function adds a new safe
method, `daemonize`, which can be used to consume an instance of `Process` which
will then not call `wait` in the destructor.

This new method is clearly documented as a leak of resources, but it must be
forcibly opted in to.

Closes #14467
auto merge of #14781 : alexcrichton/rust/issue-14724, r=brson

* os::pipe() now returns `IoResult<os::Pipe>`
* os::pipe() is now unsafe because it does not arrange for deallocation of file
  descriptors
* PipeStream::pair() has been added. This is a safe method to get a pair of
  pipes.
* Dealing with pipes in native process bindings have been improved to be more
  robust in the face of failure and intermittent errors. This converts a few
  fail!() situations to Err situations.

cc #13538
Closes #14724
[breaking-change]
auto merge of #14852 : TeXitoi/rust/relicense-shootout-pidigits, r=brson

Everyone agreed.

Related to #14248, close #14718

@brson OK?
alloc: Format heap.rs to 80-char max
alloc: Allow disabling jemalloc
alloc: Refactor OOM into a common routine
rustc: Improve span for error about using a method as a field.

libsyntax: ExprField now contains a SpannedIdent rather than Ident.

[breaking-change]
Change prints: @T -> Gc<T> , ~T -> Box<T>

Fixes #14915
Add a Syntastic plugin for Rust.
debuginfo: Correctly handle indirectly recursive types.

So far handling some indirectly recursive types, such as pointer types, has relied on LLVM metadata uniquing in a very implicit way. This could cause some inconsistencies in the debuginfo, and sometimes to hard to trace LLVM assertions.
With this commit unique type IDs and the TypeMap are used to explicitly make sure that no inconsistencies exist, and, if in the future some regression re-introduces one, give a better error message instead of the hard-to-interpret LLVM error.
Move `num_cpus` from `std::rt::util` to `std::os`. Closes #14707
std: Don't fail the task when a Future is dropped

It's a benign failure that no one needs to know about.

Closes #14892
rustc: Don't mark type parameters as exported

This ends up causing the privacy pass to get all confused, and there's nothing
inherently exported about them anyway.

Closes #14933
doc: Fix a link in the FAQ

Closes #14914
Update "use" to "uses" ln186