His 2003 play about child torture and freedom of speech became a global phenomenon. But will it offend today's audiences? The writer-director explains why he won't be changing a thing Iraq had just been invaded and MySpace had just launched, ushering in a new era of hyperlinked horror. That was the world in 2003, when Martin McDonagh's play The Pillowman premiered at the National Theatre in London. It is a creepy fab…