Auto merge of #4322 - Y0hy0h:patch-1, r=phansch
Auto merge of #4322 - Y0hy0h:patch-1, r=phansch

Improve documentation on implicit_hasher lint

Provide an example of how to fix the implicit_hasher lint.

Fixes #3475.

changelog: none

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