QUIC: fixed ACK Ranges processing. According to quic-transport draft 29, section 19.3.1: The value of the Gap field establishes the largest packet number value for the subsequent ACK Range using the following formula: largest = previous_smallest - gap - 2 Thus, given a largest packet number for the range, the smallest value is determined by the formula: smallest = largest - ack_range While here, changed min/max to uint64_t for consistency.