Macro logging_timer::finish

macro_rules! finish {
    ($timer:expr) => { ... };
    ($timer:expr, $format:tt) => { ... };
    ($timer:expr, $format:tt, $($arg:expr),*) => { ... };
}

Makes an existing timer output a 'finished' mesasge and suppresses the normal drop message. Only the first call has any effect, subsequent calls will be ignored.