In do_up() when scroll_only is TRUE, if we're at the top of the screen
in softwrap mode, it's not enough to check that edittop is on fileage.
We also need to check that firstcolumn is zero.

In do_up() when scroll_only is FALSE, if we're at the top of the screen
in softwrap mode, current_y should be zero.  This is equivalent to how,
in do_down() when scroll_only is FALSE, current_y is (editwinrows - 1)
at the bottom of the screen in softwrap mode.  Since edittop can now
be partially scrolled off the screen even when it takes up the entire
screen, checking for edittop's being equal to openfile->current->next
there no longer applies.