auto merge of #8164 : brson/rust/noportset, r=pcwalton

...haredChan.

diff --cc src/libextra/arc.rs
Simple merge

diff --cc src/test/bench/msgsend-pipes.rs
Simple merge

diff --cc src/test/bench/shootout-pfib.rs
Simple merge

diff --cc src/test/run-pass/task-comm-3.rs
Simple merge