2002-03-18  Morten Welinder  <terra@diku.dk>

	* src/workbook-control-gui.c (cb_workbook_debug_info): Add code to
	share cells in workbook.

	* src/main.c: Add --debug_share=1 option.

	* src/expr.c (expr_list_eq): New function.
	(expr_tree_sharer_new, expr_tree_sharer_destroy)
	(expr_tree_sharer_share): New functions.

	* src/position.c (cellref_hash): New function.

	* src/value.c (value_hash): New function.