Defines a new undo element format (fun . args), which
means “undo by applying fun to args”. For spreadsheet
buffers, it allows undos in the data area even though that's outside
the narrowing.
copy-region-as-kill
When copying from the print area of a spreadsheet, treat the region as
a rectangle and attach each cell's formula and printer as 'ses
properties.
yank
When yanking into the print area of a spreadsheet, first try to yank
as cells (if the yank text has 'ses properties), then as tab-separated
formulas, then (if all else fails) as a single formula for the current
cell.