Import the util crate as util rather than servo_util.

This used to conflict with the util crate from the standard library, which
has long since been removed.

The import in layout has not been changed because of a conflict with the
util mod there.

components/script/dom/servohtmlparser.rs

@@ -15,7 +15,7 @@ use dom::node::TrustedNodeAddress;
 use dom::document::{Document, DocumentHelpers};
 use parse::Parser;
 
-use servo_util::task_state;
+use util::task_state;
 
 use std::default::Default;
 use url::Url;