Rename WriterByteConversions methods

[sfackler]

The method names in std::rt::io::extensions::WriterByteConversions are
the same as those in std::io::WriterUtils and a resolve error causes
rustc to fail after trying to find an impl of io::Writer instead of
trying to look for rt::io::Writer as well.

[luqmana]

I've been using both the extension reader & writer methods fine though. Do you have a test case?

[sfackler]

use std::rt::io::{Writer, WriterByteConversions};

struct Foo;

impl Writer for Foo { 
    fn write(&mut self, _buf: &[u8]) {}
    fn flush(&mut self) {}
} 

fn main() {
    let mut f = Foo; 
    f.write_le_i32(0);
}

test.rs:12:1: 12:19 error: failed to find an implementation of trait std::io::Writer for Foo
test.rs:12  f.write_le_i32(0);
            ^~~~~~~~~~~~~~~~~~

[sfackler]

Turns out the same goes for ReaderByteConversions. @brson r?

Test case:

use std::rt::io::{Reader, ReaderByteConversions};

struct Foo;

impl Reader for Foo {
    fn read(&mut self, _buf: &mut [u8]) -> Option<uint> { None }
    fn eof(&mut self) -> bool { true }
}

fn main() {
    let mut f = Foo; 
    f.read_u8();
}

test.rs:12:1: 12:13 error: failed to find an implementation of trait std::io::Reader for Foo
test.rs:12  f.read_u8();
            ^~~~~~~~~~~~

[sfackler]

@brson had to rebase, r?