Provide map_ok and map_err method for Poll<Option<Result<T, E>>>
Provide map_ok and map_err method for Poll<Option<Result<T, E>>>

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