IPAddr.new accepts certain IPv6 literals when AF_INET is specified

If the given address is an IPv6 literal enclosed in brackets and/or with a zone ID suffix, it will be unexpectedly accepted.
All the following invocations expect AddressFamilyError.

% bundle exec irb -ripaddr
irb(main):001:0> IPAddr.new('[::]', Socket::AF_INET)
=> #<IPAddr: IPv6:0000:0000:0000:0000:0000:0000:0000:0000/ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff>
irb(main):002:0> IPAddr.new('::%eth0', Socket::AF_INET)
=> #<IPAddr: IPv6:0000:0000:0000:0000:0000:0000:0000:0000%eth0/ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff>
irb(main):003:0> IPAddr.new('[::%eth0]', Socket::AF_INET)
=> #<IPAddr: IPv6:0000:0000:0000:0000:0000:0000:0000:0000%eth0/ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff>
irb(main):004:0> IPAddr.new('::', Socket::AF_INET)
/.../ruby/ipaddr/lib/ipaddr.rb:633:in `initialize': address family mismatch (IPAddr::AddressFamilyError)
      raise AddressFamilyError, "address family mismatch"
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Reproduce the listed IPAddr.new calls in irb with -ripaddr, then inspect ipaddr.rb around line 633 where AddressFamilyError is raised. The fix is done when bracketed or zone-ID IPv6 literals supplied with Socket::AF_INET raise AddressFamilyError like the plain IPv6 literal.