2005-03-14  Morten Welinder  <terra@gnome.org>

	* src/sheet.c (sheet_finalize): New function, split out from
	sheet_destroy.
	(sheet_destroy): Just unref objects we hold refs for, i.e., no
	longer finalize.  All callers changed to unref sheet also.
	(gnm_sheet_class_init): Install sheet_finalize.  Define
	detached_from_workbook signal.