Long lines could cause a deadlock since the buffer can become full without us seeing a newline. In this case, we drop the line and continue flushing until we see our newline. The line is discarded and no response is sent to the host.
handle case where a short line, and the start of a line longer than (buffer - usbpacket) are bundled into one usb packet. the longer line will unfortunately be discarded.
USBSerial: increase RX buffer to 256 bytes to reduce likelihood of short line/long line corner case
Merge branch 'fix/deadlock_on_long_lines' into edge