Apple has posted its iOS Software Development Kit (SDK) 4.0.1, bringing with it compatibility with the latest iOS software releases. Notably, Apple is warning developers that if they have updated their iPhones to iOS 4.0.1 or their iPads to iOS 3.2.1 they will need to download and install the new SDK to continue development. Unlike the iOS 4.1 beta and accompanying SDK released yesterday, iOS SDK 4.0.1 is available to all registered developers, and…