nano: update to 2.9.7

nano: update to 2.9.7

nano 2.9.7 was released on 2018 May 15.

Release notes:

GNU nano 2.9.7 "Hvide Sande" adds the option '--afterends'
for making Ctrl+Right (the nextword function) stop at word
ends instead of beginnings, accepts multibyte letters for
the Yes/No/All answers, does emergency saves of changed
buffers in the unlikely event that nano crashes, adds the
until-now missing bindable function 'linenumbers', and
renames the toggles 'constupdate' to 'constantshow' and
'cuttoend' to 'cutfromcursor', for consistency with the
corresponding options -- adjust your nanorc files soon.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>
(cherry picked from commit d9e9b59159309449df7a7a6d4ab87980dc16eac2)