* restore definition of ip_addr (=ipv4_addr) when IPv6 is not enabled
* overload IPAddress:operator == and != to avoid ambiguousness
* brings lwIP's INADDR_NONE (which is IPv4 255.255.255.255, suposed to be invalid address but it is)
* inet_aton is a lwIP define, rename Ethernet DNS implementation of this to prevent name collision
that's because IPAddress now includes lwip/inet.h
Use platform.local.txt to add -Werror to GCC for the build of all
code. Any warnings on a submitted patch will cause an error.
Several examples and libraries had warnings/errors (missing returns
on functions, types, etc.). Clean those up with this commit as well.
