auto merge of #11808 : huonw/rust/std-visible-types, r=brson

These are either returned from public functions, and really should
appear in the documentation, but don't since they're private, or are
implementation details that are currently public.

src/libstd/io/mod.rs

@@ -1268,7 +1268,7 @@ pub trait Acceptor<T> {
 /// The Some contains another Option representing whether the connection attempt was succesful.
 /// A successful connection will be wrapped in Some.
 /// A failed connection is represented as a None and raises a condition.
-struct IncomingConnections<'a, A> {
+pub struct IncomingConnections<'a, A> {
     priv inc: &'a mut A,
 }