Add support for iPad4,6 (iPad mini 2G new model)
irecovery: Improve printing of hex values for /deviceinfo command
Lower error message severity if a nonce is not found to a warning
Add libusb error to debug message when connecting to a device failed
Don't call libusb_exit() in irecv_open_with_ecid() on error

The helper might be used multiple times and the library should not
cause deinitialization of libusb before the user calls irecv_exit().
Only output debug information in irecv_copy_nonce_with_tag() on error