don't leak the async_context

don't leak the async_context

	* libsoup/soup-message-io.c (soup_message_io_unpause): don't leak
	the async_context

	* libsoup/soup-server.c (soup_server_quit): disconnect the
	"new_connection" handler.
	(soup_server_get_async_context): Convenience method to return the
	server's async_context.

	* libsoup/soup-server-message.c: don't circularly ref the server,
	there's no need anyway.

	* libsoup/soup-session.c (soup_session_get_async_context):
	Convenience method to return the session's async_context.

	* libsoup/soup-session-async.c (queue_message): call run_queue in
	the session's async_context, not the main context.
	(send_message): don't leak the async_context

	* libsoup/soup-session-sync.c (queue_message_thread): don't leak
	the async_context

	* tests/context-test.c: test that SOUP_SESSION_ASYNC_CONTEXT works
	and doesn't leak

svn path=/trunk/; revision=954