fix link on std::result::Result
fix link on std::result::Result

The link is broken here: <https://doc.rust-lang.org/std/io/#types>.

Looks like crate documentation generator uses only first paragraph of the module documentation and 
so doesn't resolve the link defined below.
GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust