undo_add_change
int undo_add_change(struct line *, int, int);
undo_add_change(region.r_linep, region.r_offset, region.r_size);
undo_add_change(region.r_linep, region.r_offset, region.r_size);
undo_add_change(curwp->w_dotp, curwp->w_doto, size);
undo_add_change(curwp->w_dotp, curwp->w_doto, size);
undo_add_change(curwp->w_dotp, curwp->w_doto, size);