Fixed Result type parameters in doc comment.

src/libcore/result.rs

@@ -10,7 +10,7 @@
 
 //! Error handling with the `Result` type
 //!
-//! `Result<T>` is the type used for returning and propagating
+//! `Result<T, E>` is the type used for returning and propagating
 //! errors. It is an enum with the variants, `Ok(T)`, representing
 //! success and containing a value, and `Err(E)`, representing error
 //! and containing an error value.