My contribution to lwIP

All my contributed code to lwIP is now merged in the lwIP open-source development hosted on Savannah. I try to commit changes regularly.

• Infineon C16x port (using the lightweight callback API of lwIP).
• Cirrus/Crystal Semiconductor CS8900A MAC/PHY Ethernet driver (tested in combination with the 16-bit C16x processor).
• Ethernet ARP layer
• DHCP client