close() is isClosed() not synchronized on socket state

Socket, ServerSocket, and DatagramSocket's close() and isClosed() methods
aren't property synchronized so it's possible for isClosed() to return
'false' even though the socket has just been closed.

This issue can be demonatrated with test/java/net/Socket/InheritTimeout.java
if the following is uncommented :-

// Socket.isClosed isn't synchronized - when this is
                // fixed uncomment the following
                //throw e;

###@###.### 2001-11-08