Better support for HTTPBodyStream

Since NSURL session by default uses HTTPBodyStreams, this is needed to support anything that uses NSURLSession, including AFNetworking 2.0. Whee!
I slightly prefer:

        case NSStreamEventHasBytesAvailable:
        {
            [...]
        }
            break;

or

        case NSStreamEventHasBytesAvailable: {
            [...]
        }
            break;

but I don't know that it comes up often enough to want to bother standardizing it, other than "keep it consistent within a single file and preferably within a single project."