Macro lrs::errln!

Like println but write to stder.

Syntax

( $ fmt : expr ) => {
write ! ( :: std:: fd:: STDERR , concat ! ( $ fmt , "\n" ) ) } ; (
$ fmt : expr , $ ( $ arg : tt ) * ) => {
write ! ( :: std:: fd:: STDERR , concat ! ( $ fmt , "\n" ) , $ ( $ arg ) * ) }
;