Enhance timers to create ports

In addition to being able to sleep the current task, timers should be able to
create ports which get notified after a period of time.

Closes #10014
Rewrite boxed_region/memory_region in Rust

This drops more of the old C++ runtime to rather be written in rust. A few
features were lost along the way, but hopefully not too many. The main loss is
that there are no longer backtraces associated with allocations (rust doesn't
have a way of acquiring those just yet). Other than that though, I believe that
the rest of the debugging utilities made their way over into rust.

Closes #8704
Make addl_lib_search_paths a HashSet (Closes #7718).
Implement another error code found on windows.

Closes #8811
Make the documentation for std::task::spawn_sched render correctly.

Currently each line is a separate bullet point in a list: http://static.rust-lang.org/doc/master/std/task/fn.spawn_sched.html
make the bottom type immediate

Before:

    define void @_ZN3bar19h9d9b965357abc043af4v0.0E({}* noalias nocapture readnone sret, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone)

After:

    define void @_ZN3bar19h9d9b965357abc043af4v0.0E({ i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone)
rustpkg: Build dependencies into the correct workspace when using --rust-path-hack

When invoked with the --rust-path-hack flag, rustpkg was correctly building
the package into the default workspace (and not into the build/ subdirectory of the
parent directory of the source directory), but not correctly putting the output
for any dependencies into the default workspace as well.

Spotted by Jack.
mark bounds check failures as the cold path

LLVM is unable to determine this for most cases.

http://llvm-reviews.chandlerc.com/D2034 needs to land upstream before
this is going to have an effect. It's harmless to start generating the
expect hint now.
Allow fail messages to be caught, and introduce the Any trait

Some code cleanup, sorting of import blocks

Removed std::unstable::UnsafeArc's use of Either

Added run-fail tests for the new FailWithCause impls

Changed future_result and try to return Result<(), ~Any>.

- Internally, there is an enum of possible fail messages passend around.
- In case of linked failure or a string message, the ~Any gets
  lazyly allocated in future_results recv method.
- For that, future result now returns a wrapper around a Port.
- Moved and renamed task::TaskResult into rt::task::UnwindResult
  and made it an internal enum.
- Introduced a replacement typedef `type TaskResult = Result<(), ~Any>`.
auto merge of #9967 : Kimundi/rust/fail_cause_two, r=huonw

# Summary

This PR allows the cause of a failure to be received in a task's future result and as the `Err` case of `task::try`, and also implements dynamic typing in form of an `Any` trait.

# Task failure

- `fail!` and related macros now accept 5 kinds of types: `~str`, `&'static str`, `std::send_str::SendStr`, `~std::any::Any` and `~T` where `T: Any + Send + 'static`
- `std::task::TaskResult` got transformed into an internal enum `std::rt::task::UnwindResult`,  and it's `Failure` variant now contains a value of enum type `UnwindReason`:
  - `UnwindReasonStr(SendStr)` maps to failing with a value of type `~str`, `&'static str` or `SendStr`.
  - `UnwindReasonAny(~Any)` maps to failing with an `~Any` or `~T` with `T: Send + 'static`.
  - `UnwindReasonLinked` maps to failing because the task got killed by linked failure.
- Instead, `std::task::TaskResult` is now a typedef for `Result<(), ~Any>`, and both `TaskBuilder`'s `future_result()` and `task::try` now work with a value of this type.
- `future_result()` no longer returns a `Port<TaskResult>`, instead it returns a wrapper `TaskResultPort` that implements `GenericPort` and `Peekable`, and which lazily allocates a `~` box and casts to `~Any` in case of failure with a `SendStr` or linked failure (for the latter case a unit struct `LinkedFailure` got added.)
- Because `fail!` collapses both `~str` and `&'static str` into a `SendStr`, checking if a task error value is a string will just require a `.is::<SendStr>()` check, with `~str` and `&'static str` only being possible in case of an explicit `fail!(~~"...")` or `fail!(~ (&"...") as ~Any)`:

# Any

- In order to allow failing with arbitrary data, the `Any` trait got implemented.
- It is being used in form of a trait object, usually `~Any` or `&Any`.
- `&Any`, `~Any` and `&mut Any` have a few extension methods implemented on them:
  - `is<T>(self) -> bool` returns true if the `Any` object contains type `T`
  - `as_ref<T>(self) -> Option<&T>` returns a reference to the contained type, if it is `T`
  - `as_mut<T>(self) -> Option<&mut T>` returns a mutable reference to the contained type, if it is `T`
  - `move<T>(self) -> Option<~T>` allows to get the `~T` out of an `~Any` again.
- `Any` currently uses type descriptors as a type id for comparisons, which is 
    - not reliable, as it is not guaranteed that every type has only one type descriptor.
    - But safe, as no two types share the same type descriptor.
- The implementation also a few `transmute`s, mostly to cast a `*Void` of the wrapped type into it's actual type `&T`, `&mut T` or `~T`.

# Other changes

- `std::unstable::UnsafeArc::try_unwrap` no longer uses `Either`, bringing us one step closer to removing that type.
- A few of the touched modules got their import lines sorted.
- A few stylistic cleanups here and there.
auto merge of #10083 : alexcrichton/rust/timer-port, r=pcwalton

In addition to being able to sleep the current task, timers should be able to
create ports which get notified after a period of time.

Closes #10014
syntax: remove dead @mut Visitor impl (only used in tests).

Also, move some code only uses in the tests into the test module, and
replace some needless @mut ~[] with plain ~[].
auto merge of #10093 : alexcrichton/rust/issue-8811, r=pcwalton

Closes #8811
auto merge of #10094 : alexcrichton/rust/issue-8704, r=pcwalton

This drops more of the old C++ runtime to rather be written in rust. A few
features were lost along the way, but hopefully not too many. The main loss is
that there are no longer backtraces associated with allocations (rust doesn't
have a way of acquiring those just yet). Other than that though, I believe that
the rest of the debugging utilities made their way over into rust.

Closes #8704
auto merge of #10107 : thestinger/rust/immediate, r=huonw
auto merge of #10089 : pythonesque/rust/issue-7718, r=catamorphism

Seems pretty straightforward, but please let me know if I'm doing something wrong or the test needs to be rewritten.
Remove the extension traits for Readers/Writers

These methods are all excellent candidates for default methods, so there's no
need to require extra imports of various traits.
auto merge of #10079 : alexcrichton/rust/no-reader-util, r=brson

These methods are all excellent candidates for default methods, so there's no need to require extra imports of various traits. Additionally, this was able to remove all the weird underscores after the method names. Yay!
Handle another possible error in a unix pipe test

This cropped up on the bsd bot, and if it's an error that gets thrown then it's
fine to just whitelist another type of error in the test.
auto merge of #10095 : huonw/rust/master, r=cmr

Currently each line is a separate bullet point in a list: http://static.rust-lang.org/doc/master/std/task/fn.spawn_sched.html