Issue 1068 socket getifaddrs

Initial implementation of Socket.getifaddrs [2.1]. 

This implementation is not 100% complete yet. There are a couple of methods that was not implemented (`flags` and `dstaddr` I'm still working on it) and also `netmask` method support only ipv4 address (returning nil for ipv6 - I'm still working on it as well).

#1068