PR libgcj/15430
	* gnu/java/net/natPlainSocketImplPosix.cc (throw_on_sock_closed): New
	function.
	(accept): Call it.
	(close): Call shutdown before closing.
	(read()): Call read_helper with proper parameters.
	(read(buffer, int, int)): Likewise.
	(read_helper):  Pass pointer to the PlainSocketImpl, remove native_fd
	and timeout parameters.  Make prototype to match. Use 
	pointer to PlainSocketImpl to access members. Call throw_on_sock_closed
	in two places.

From-SVN: r107036