Version 2.4.0

• Added PingClient class and example
• Added EtherSia::rejectPacket()
• Added MACAddress::operator==
• Added MACAddress::isIPv6Multicast()
• Added checks for Ethernet source and destination address
• Added support for constructing IPv6Address and MACAddress from a flash string
• Switched to using SPISettings class to configure SPI
• Set Traffic Class and Flow Label to 0 when sending replies
• Changed TFTPServer::handleRequest() to return boolean
• Use link local address when sending, if there is no global IP
• Bug fix for Neighbour Discovery for link local address
• Bug fix for neighbour discovery setting wrong source address