Implement Socket#reuse_port on Windows

[stakach]

I think this is a better solution than having runtime errors on windows and having to write code like this for multi-platform support

    # example of what needs to be written before this commit is merged
    @socket = UDPSocket.new @address.family
    @socket.reuse_address = true
    {% unless flag?(:win32) %}
      @socket.reuse_port = true
    {% end %}

noting that windows SO_REUSEADDR == linux SO_REUSEPORT
and on windows, reuse of the address component of a binding is always allowed

I've also changed the socket defaults to use SO_EXCLUSIVEADDRUSE
as per the docs:

[HertzDevil]

Does this PR unblock the following spec?

crystal/spec/std/http/server/server_spec.cr

Lines 84 to 93 in 14bfa99

	pending_win32 "reuses the TCP port (SO_REUSEPORT)" do
	s1 = HTTP::Server.new { |ctx| }
	address = s1.bind_unused_port(reuse_port: true)
	s2 = HTTP::Server.new { |ctx| }
	s2.bind_tcp(address.port, reuse_port: true)
	s1.close
	s2.close
	end

Also this error shows up on CI:

Unhandled exception in spawn: setsockopt 4: An invalid argument was supplied. (Socket::Error)
  from src\crystal\system\win32\socket.cr:322 in 'system_setsockopt'
  from src\socket.cr:403 in 'setsockopt'
  from src\socket.cr:413 in 'setsockopt_bool'
  from src\socket.cr:411 in 'setsockopt_bool'
  from src\socket.cr:275 in 'reuse_address='
  from src\socket\tcp_server.cr:40 in 'initialize:reuse_port'
  from src\socket\tcp_server.cr:36 in 'new:reuse_port'
  from src\http\server.cr:213 in 'bind_tcp'
  from spec\std\http\web_socket_spec.cr:377 in '->'
  from src\fiber.cr:146 in 'run'
  from src\fiber.cr:98 in '->'

[stakach]

@HertzDevil in regards to the error

  from src\socket.cr:411 in 'setsockopt_bool'
  from src\socket.cr:275 in 'reuse_address='

it looks like my macro finished isn't working as reuse_address should be a no-op

It should also unblock that http server spec reuses the TCP port I'll update that spec

[straight-shoota]

Yeah macro finished didn't work as an override the way you had implemented it. It would define these methods after everything else, but still in the module scope. So it could not override the defs in the including scope.

[stakach]

needed macro included; macro finished switched to @HertzDevil's wasm approach
Specs passing now which is nice