in edit_scroll(), redraw the lines before and after the scrolled region

in edit_scroll(), redraw the lines before and after the scrolled region
even if the scrolled region was only one line; this fixes a display
problem that occurs after doing a search that scrolls the screen down
one line and leaves the cursor on the last line of the screen, in which
case we need to update the line after the scrolled region

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@3254 35c25a1d-7b9e-4130-9fde-d3aeb78583b8