MMTk 0.11.0

GC Plans

• Introduced a new work packet type SFTProcessEdges. Most plans now use SFTProcessEdges for tracing objects,
  and no longer need to implement any plan-specific work packet. Mark compact and immix plans still use their own
  tracing work packet.

Policies

• Fixed a bug that ImmixCopyContext did not set the mark bit after copying an object.
• Fixed a bug that MarkCompactSpace used ObjectReference and Address interchangably. Now MarkCompactSpace
  properly deals with ObjectReference.

API

• is_mapped_object() is superseded by is_in_mmtk_spaces(). It returns true if the given object reference is in
  MMTk spaces, but it does not guarantee that the object reference actually points to an object.
• is_mmtk_object() is added. It can be used to check if an object reference points to an object (useful for conservative stack canning).
  is_mmtk_object() is only availble when the is_mmtk_object feature is enabled.

Misc

• MMTk core now builds with stable Rust toolchains (minimal supported Rust version 1.57.0).
• Fixed a bug that MMTk may not map metadata and SFT for an object reference if the object reference is in a different
  chunk from the allocated address.
• Added trait Region and struct RegionIterator<R> to allow convenient iteration through memory regions.