IPv6 Support

[maxsharabayko]

Check if IPv6 works well and fix bugs if any.

• a potential seg fault there if user uses ipv6 and accepts a "connection" assuming it is from an ipv4 address
  

  srt-xtransmit/xtransmit/srt_socket.cpp

  Line 137 in c197de3

  sockaddr_in scl;