Malcolm Young, guitarist and co-founder of AC/DC, died Saturday at the age of 64 after a battle with dementia. Martyn Goodacre Hulton Archive By Daniel Kreps Malcolm Young, guitarist and co-founder of AC/DC, died Saturday at the age of 64. Young had been suffering with dementia for the past three years, an illness that forced his retirement from the Rock and Roll Hall of Fame-inducted band he…