- Fix a problem with zooming caused by the new item-bar enhancements.
- Remove gnumeric-sheet.h from a number of places that it had no reason to be.
- Move all of the row/col pos/offset cache into GnumericSheet.  WARNING
  I do not populate all of it yet.

2000-01-26  Jody Goldberg <jgoldberg@home.com>

	* src/sheet-view.c (sheet_view_set_zoom_factor) : Keep the cursor in
	  the same place and recompute the alignments for everything.

	* src/item-cursor.c (item_cursor_set_bounds) : New function.

	* src/gnumeric-sheet.h : Add more orthogonal structure for caching
	  common row/col bounds and their canvas offsets.

	* src/gnumeric-sheet.c (gnumeric_sheet_create) : Init the new members.
	(gnumeric_sheet_filenames_dropped) : Keep the canvas private.
	(gnumeric_sheet_make_cell_visible) : Add 'force_scroll' argument.

	* src/clipboard.c (clipboard_release) : It is possible to have no
	  styles associated with a region.

	* src/item-grid.c : Remove overlapping cache of bounding rows/cols and
	  offsets.  Use the superset in GnumericSheet.
	 (item_grid_find_{row, col}) : Support sliding backwards.