std::str stabilization breaking changes

[seb-m]

It seems that #19741 is breaking this code, for instance std::str::ScalarValue doesn't exist anymore:

rustc-serialize-0.1.3/src/json.rs:205:25: 205:36 error: unresolved import `std::str::ScalarValue`. There is no `ScalarValue` in `std::str`
/Users/seb/.cargo/registry/src/github.com-1ecc6299db9ec823/rustc-serialize-0.1.3/src/json.rs:205 use std::str::{FromStr, ScalarValue};
                                                                                                                         ^~~~~~~~~~~
error: aborting due to previous error
Could not compile `rustc-serialize`.

[alexcrichton]

Fixed in 97c3783, thanks!