Transfer error - timeout (-7) altough everything works ok?

DeviceProxy_LibUSB.cpp:

function :receive_data
case - USB_ENDPOINT_XFER_INT
This version reports a timeout, alrough older version code had a `hack` that implies that a timeout is a "ok" response. Older version code:

``` C
 if (rc==LIBUSB_ERROR_TIMEOUT){free(*dataptr);*dataptr=NULL;*length=0;return;}
```
