Update nano editor to version 4.0.

Release notes at
http://git.savannah.gnu.org/cgit/nano.git/plain/NEWS?h=v4.0

 2019.03.24 - GNU nano 4.0 "Thy Rope of Sands"
 * An overlong line is no longer automatically hard-wrapped.
 * Smooth scrolling (one line at a time) has become the default.
 * A newline character is no longer automatically added at end of buffer.
 * The line below the title bar is by default part of the editing space.
 * Option --breaklonglines (-b) turns automatic hard-wrapping back on.
 * Option --jumpyscrolling (-j) gives the chunky, half-screen scrolling.
 * Option --finalnewline (-f) brings back the automatic newline at EOF.
 * Option --emptyline (-e) leaves the line below the title bar unused.
 * <Alt+Up> and <Alt+Down> now do a linewise scroll instead of a findnext.
 * Any number of justifications can be undone (like all other operations).
 * When marked text is justified, it becomes a single, separate paragraph.
 * Option --guidestripe=<number> draws a vertical bar at the given column.
 * Option --fill=<number> no longer turns on automatic hard-wrapping.
 * When a line continues offscreen, it now ends with a highlighted ">".
 * The halfs of a split two-column character are shown as "[" and "]".
 * A line now scrolls horizontally one column earlier.
 * The bindable functions 'cutwordleft' and 'cutwordright' were renamed
   to 'chopwordleft' and 'chopwordright' as they don't use the cutbuffer.
 * The paragraph-jumping functions were moved from Search to Go-to-Line.
 * Option --rebinddelete is able to compensate for more misbindings.
 * Options --morespace and --smooth are obsolete and thus ignored.
 * The --disable-wrapping-as-root configure option was removed.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>