* fhandler_socket.cc (fhandler_socket::bind): Don't run explicit

	* fhandler_socket.cc (fhandler_socket::bind): Don't run explicit
	local socket test in SO_REUSEADDR case on systems supporting
	enhanced socket security.  Explain why.  Only call address_in_use
	for AF_INET sockets.
	* net.cc (cygwin_setsockopt): Don't call setsockopt to set SO_REUSEADDR
	on systems supporting enhanced socket security.  Add comment.
	* wincap.h (wincaps::has_enhanced_socket_security): New element.
	* wincap.cc: Implement above element throughout.