Bug #96006 for Device-ELM327: [PATCH] Make ReadResponse() more robust

Hello, I was trying to use Device::ELM327 with obdgpslogger's obdsim which simulates an ELM327 device, see: http://icculus.org/obdgpslogger/ ReadResponse() was failing to read the response correctly from obdsim as it seemed it would get an empty read (0 bytes returned) before the actual end of the response. This would cause it to fail to even detect obdsim as an ELM327 device. I have attached a patch that changes ReadResponse() to (hopefully) be more robust. Instead of a zero-byte read signaling the end of the response, it watches for the '>' character on a line by itself. In the case of zero-byte reads, ReadResponse() will retry each read up to a maximum number of retries. There is an increasingly longer delay between each retry in the hopes that we can recover quickly in the case of a small ECU delay but accommodate for a longer ECU delay. I've run this patch successfully against obdsim and against an actual ELM327 device (over USB) that I have. It was not attached to a car at the time however so testing was limited. Thanks, Jason