Microsoft's proper preview event for the next big release of Windows Phone may be mere hours away, but there's still time for a bit of good old fashioned web sleuthing before then. Latest on our radar is this Microsoft Developer Network page listing out all the APIs in Silverlight for Windows Phone 7.1. That's right, your eyes do not deceive you, there's a whole extra decimal added to the OS number, ostensibly signifying the move to the Mango update we're all so hungry for. We'd previously heard the moniker of Windows Phone 7.5 bandied about, but that was based on supposition more than anything else, and a .1 upgrade makes sense in light of the curent 7.0.7 version number. Fuller details will be forthcoming later on today, but for now, pencil in the number 7.1 alongside the dream specs of your next Windows Phone.