Add librustc, libsyntax to rust-src distribution.
Add librustc, libsyntax to rust-src distribution.

graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust