Fixed bug 2068 (Dragging icons adjusts scroll area in a way
	that causes immediate scrolling)

	Fixed bug 3402 (Dragging singleton icon to edge of window in
	manual layout mode puts it back at top-left)

	Fixed bug 3405 (Dropping an icon into empty manual-layout
	window always puts it at top-left)

	Fixed bug 3570 (Relayout glitch after removing an item from
	a view)

	I had earlier started to fix these by trying to save and
	restore the scroll position per directory. But this path
	turned evil, and I gave up on it. There is still some
	partly-implemented work from my start in the evil direction,
	which I will remove in my next checkin.

	The new fix was to always include the visible white space
	when recomputing the icon container's scroll region, unless
	a caller has specifically requested not to.

	* libnautilus-extensions/nautilus-icon-container.h:
	* libnautilus-extensions/nautilus-icon-container.c:
	(nautilus_icon_container_reset_scroll_region): New function,
	sets a flag in the details struct that's respected in the
	next scroll region update.
	(reset_scroll_region_if_not_empty): New helper function,
	calls _reset_scroll_region unless container is empty.
	(nautilus_icon_container_update_scroll_region_include_visible_area):
	Removed this function; its equivalent is to call reset_scroll_region
	before calling update_scroll_region.
	(nautilus_icon_container_update_scroll_region): Now that the
	_include_visible_area variant is gone, merged the local function
	update_scroll_region with this public one. It decides whether to
	include the visible area or not based on the flag set by
	_reset_scroll_region (also, it never includes the visible area
	if the container is empty).
	(nautilus_icon_container_set_auto_layout): Reset the scroll region
	when changing the auto_layout state.
	(nautilus_icon_container_sort): reset the scroll region before
	sorting.

	* libnautilus-extensions/nautilus-icon-dnd.c: (handle_local_move):
	Call nautilus_icon_container_update_scroll_region instead of
	_update_scroll_region_include_visible_area, which no longer exists.

	* libnautilus-extensions/nautilus-icon-private.h: Store flag for
	resetting scroll region in details; eliminate prototype for
	nautilus_icon_container_update_scroll_region_include_visible_area.

	* src/file-manager/fm-directory-view.h:
	* src/file-manager/fm-directory-view.c:
	(fm_directory_view_initialize_class), (done_loading),
	(fm_directory_view_begin_loading), (fm_directory_view_end_loading):
	Added end_loading signal that's sent when a directory is finished
	loading, parallel to existing begin_loading signal.

	* src/file-manager/fm-icon-view.c:
	(fm_icon_view_add_file): Reset the scroll region for the first
	icon added when loading a directory.
	(fm_icon_view_begin_loading), (fm_icon_view_end_loading):
	Remember that we're loading, so	fm_icon_view_add_file can test correctly.
	(set_sort_criterion_by_id): Bail out early if state hasn't changed.
	(switch_to_manual_layout): Bail out early if state hasn't changed.
	Also, reset scroll region before switching to manual layout.
	(fm_icon_view_initialize_class): Attach fm_icon_view_end_loading to
	virtual function slot.