audiod: Fix status item parsing for long status items.

audiod: Fix status item parsing for long status items.

This was broken since audiod started to use the buffer tree API. Actually there are
two bugs which are both fixed by this patch:

	- for_each_stat_item() copies the remaining part of the buffer containing
	the incomplete part of the last status item to the beginning of the buffer.
	This is necessary if the buffer tree API is not used but messes up the buffer
	contents if it _is_ used. Move this memmove() 	call from for_each_status_item(),
	which is called from audiod.c and gui.c,  to gui.c, as only gui.c needs it.

	- Secondly, audiod.c called btr_node_status() with an minimum input queue
	size of zero, which is does not work if a status item crosses a buffer
	boundary. In this case for_each_status_item() will only ever see the first buffer
	containing the incomplete status item, hence it can never make progress.
	Fix this by introducing  the min_iqs field of struct status_task. Set  this field
	to non-zero if the full buffer size was returned by for_each_status_item(),
	indicating that the next status item is spread out over two or more buffers.