Evaluate # fn in docs

I searched for times when we were hiding functions with # in the documentation,
and fixed them to not use it unless neccesary.

I also made random improvements whenever I changed something. For example,
I changed Example to Examples, for consistency.

Fixes #13423

src/libcore/prelude.rs

@@ -21,11 +21,7 @@
 //! # Example
 //!
 //! ```ignore
-//! # fn main() {
-//! #![feature(globs)]
-//!
 //! use core::prelude::*;
-//! # }
 //! ```
 
 // Reexported core operators