MMTk 0.10.0

GC Plans

• Removed plan-specific copy contexts. Now each plan needs to provide a configuration for
  GCWorkerCopyContext (similar to how they config Mutator).
• Fixed a bug that needs_log_bit was always set to true for generational plans, no matter
  their barrier used the log bit or not.
• Fixed a bug that we may overflow when calculating get_available_pages().

Policies

• Refactored copy context. Now a copying policy provides its copy context.
• Mark sweep and mark compact now uses ObjectIterator for linear scan.

Scheduler

• Introduced GCController, a counterpart of GCWorker, for the controller thread.
• Refactored GCWorker. Now GCWorker is seperated into two parts, a thread local part GCWorker
  which is owned by GC threads, and a shared part GCWorkerShared that is shared between GC threads
  and the scheduler.
• Refactored the creation of the scheduler and the workers to remove some unnecessary Option<T> and RwLock<T>.

API

• Added process_bulk() that allows bindings to pass options as a string of key-value pairs.
• ObjectModel::copy() now takes CopySemantics as a parameter.
• Renamed Collection::spawn_worker_thread() to spawn_gc_thread(), which is now used to spawn both GC worker and
  GC controller.
• Collection::out_of_memory() now takes AllocationError as a parameter which hints the binding
  on how to handle the OOM error.
• Collection::out_of_memory() now allows a binding to return from the method in the case of a non-critical OOM.
  If a binding returns, alloc() will return a zero address.

Misc

• Added ObjectIterator that provides linear scanning through a region to iterate
  objects using the alloc bit.
• Added a feature work_packet_stats to optionally collect work packet statistics. Note that
  MMTk used to always collect work packet statistics.
• Optimized the access to the SFT map.
• Fixed a few issues with documentation.
• The example header file mmtk.h now uses the prefix mmtk_ for all the functions.