Replace all uses of rust-intrinsic ABI with calls to unstable::intrinsics
auto merge of #6639 : osaut/rust/arc-clean, r=brson

* Add ARC::get method and implements the function from it.
* Add an example showing a simple use of ARC.

Update PR #6622 to avoid git noise.

I will remove the function get later.
core: Update clone docs
core::rt: Rename WorkQueue methods, remove extra push method
core::rt: Put a lock on the work queue
core::rt: Add MessageQueue type

This is the queue used to send messages to Schedulers
core::rt: Queues MessageQueue and WorkQueue are cloneable
core:rt:: Rename LocalServices to Task
core::rt: Add Local trait
core::rt: Store Task as a ~ pointer
rt: Rename rust_initialize_global_state to rust_initialize_rt_tls_key
core::rt: Move some TLS functions from local_sched to local_ptr
core::rt: Move more TLS functionality into local_ptr
core::rt: Make local_sched a wrapper around Local
core::rt: Convert users of local_sched to Local trait
core::rt: Remove local_sched module
core::rt: Implement Local for Task
core::rt: Convert unsafe_borrow_io to a Local impl
auto merge of #6372 : brson/rust/intrinsics, r=catamorphism

...s
auto merge of #6528 : brson/rust/docs, r=brson

Remove the uncommon term 'object tree' in favor of 'value'.