Nimbuzz has released an update to its instant messaging and voice-over-IP application adding support for background Internet calling on multitasking-capable iOS 4 devices. With Nimbuzz 2.0.1 users of the iPhone 3GS, iPhone 4 and third-generation iPod touch can now receive and answer VoIP calls even when the Nimbuzz app is not actively running in the foreground. Users can also continue to carry on a conversation via Nimbuzz while accessing other apps…