Reading from stdin with libuv on separate task fails on windows

[luqmana]

foo.rs:

use std::io;

fn main() {
    do spawn {
        let b = io::stdin().read_byte().unwrap();
        println!("Got: {}", b as char);
    }
}

$ rustc.exe foo.rs
$ foo.exe
task '<unnamed>' failed at 'stream alloc_cb called more than once', C:\MinGW\msys\1.0\home\Luqman\rust\src\libstd\option.rs:113
task '<main>' failed at 'killed by linked failure', C:\MinGW\msys\1.0\home\Luqman\rust\src\libstd\rt\kill.rs:639

Adding #[no_uv] makes it works as expected:

$ foo.exe
a
Got: a

Ping @alexcrichton