allow unknown features in the log crate.

src/liblog/lib.rs

@@ -163,6 +163,8 @@
        html_favicon_url = "http://www.rust-lang.org/favicon.ico",
        html_root_url = "http://doc.rust-lang.org/nightly/",
        html_playground_url = "http://play.rust-lang.org/")]
+
+#![allow(unknown_features)]
 #![feature(slicing_syntax)]
 #![feature(box_syntax)]
 #![deny(missing_docs)]