With the announcement of iPhone OS 4.0 last week, the big question on the lips of older iPhone owners was “which devices will support multitasking”. The official answer at the time was that the iPhone 3GS is as far back as support will be offered, with the reason suggested by John Gruber that the 3GS has 256mb of RAM, while all previous devices have only 128mb. There is a small ray of hope for users of the older models however, in the predictable form of a jailbreak option. For users willing to take this risk and live outside Apple’s big brother-esque world, the optino to enable multitasking may be as simple…