RefCell: document panics in Clone, PartialEq, PartialOrd, Ord. Fixes #47400
RefCell: document panics in Clone, PartialEq, PartialOrd, Ord. Fixes #47400

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