* fhandler_socket.cc (address_in_use): Disable. Add comment.

	* fhandler_socket.cc (address_in_use): Disable.  Add comment.
	(fhandler_socket::bind): Change comment to explain setting the
	SO_EXCLUSIVEADDRUSE socket option.  Remove code which checks for
	address in use.
	* net.cc (cygwin_setsockopt): Never set SO_REUSEADDR option.  Improve
	comment to compensate for the deleted comment in fhandler_socket::bind.
	* wincap.cc: Throughout, drop has_enhanced_socket_security from wincaps.
	* wincap.h (struct wincaps): Drop has_enhanced_socket_security flags
	and method.