The printf formatting mini-language actually allows you
to pass a '*' character in place of the fill width specification,
in which case it eats one of the passed in arguments and uses it
as width, so implement that.
It's kinda funny how I can make a mistake like this in Serenity and then
get so used to it by spending lots of time using this API that I start to
believe that this is how printf() always worked..
