Fix links in rustdoc book.
Fix links in rustdoc book.

Due to a change in how mdbook generates section anchors, headers
with non-alphabetic characters now start with "a".

GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust