Consider adding a .foreach()-like method to Iterator

[alexcrichton]

Proposed in rust-lang/rfcs#582 and rust-lang/rfcs#1064, the Iterator trait could have a .foreach method which drains the iterator immediately and runs a closure on each element to concisely do so without a for loop.

[steveklabnik]

should be over here instead: rust-lang/rfcs#1070

[alexcrichton]

Oh oops! I meant for this to be in rust-lang/rfcs but wasn't paying attention...