1998-10-05  Miguel de Icaza  <miguel@nuclecu.unam.mx>

	* src/cell.c (cell_modified): New function, used to tag a modified
	cell in a sheet.

	* src/fn-math.c (gnumeric_average): Display error on division by
	zero.  Make the code not depend on the types returned by
	gnumeric_sum and gnumeric_count.
	(callback_function_sum): Keep sum as integers as long as
	possible instead of using floating point all the time.