Add recover_missing_comment_in_span() and rewrite_missing_comment()
Add recover_missing_comment_in_span() and rewrite_missing_comment()

rust-lang/rustfmt,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,SingingTree/rustfmt,graydon/rust,SingingTree/rustfmt,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,rust-lang/rustfmt