Reexport of std::rt::io::extensions::ReaderUtil is broken

[sfackler]

use std::rt::io::ReaderUtil;
use std::rt::io::mem::MemReader;

fn foo() {
    let mut buf = MemReader::new(~[]);
    buf.read_bytes(1);
}

~/temp ❯ rustc --lib test.rs
test.rs:6:1: 6:19 error: failed to find an implementation of trait std::io::Reader for std::rt::io::mem::MemReader
test.rs:6   buf.read_bytes(1);
            ^~~~~~~~~~~~~~~~~~

If I modify ReaderUtil to add an underscore to read_bytes to avoid the name conflict, I get this error instead:

test.rs:6:1: 6:19 error: type `std::rt::io::mem::MemReader` does not implement any method in scope named `read_bytes_`
use std::rt::io::extensions::ReaderUtil;
test.rs:6   m.read_bytes_(10);
            ^~~~~~~~~~~~~~~~~~

But if I make extensions a public module and use ReaderUtil from there, everything works:

use std::rt::io::extensions::ReaderUtil;
use std::rt::io::mem::MemReader;

fn foo() {
    let mut buf = MemReader::new(~[]);
    buf.read_bytes(1);
}