auto merge of #8074 : thestinger/rust/iterator, r=cmr

d7c9bb4 r=alexcrichton
7ae17e0 r=huonw

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

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

diff --cc src/libstd/hashmap.rs
Simple merge