New code from lwip project

lwip repo:
63038e0 Restore DHCP relay test packet numbers

lwip-contrib repo:
47ab4b0 httpd: fix memory leak when LWIP_HTTPD_SUPPORT_REQUESTLIST==1 and connection is closed while trying to parse a request (should not happen on correct connections)
80ae68d changed win32 project files to MSVC9/Visual C++ 2008 and renamed the directory accordingly; added .gitignore to ignore all the MSVC build files
af57a58 Updated win32 example port project to include changed PPP files