Update nano to 2.8.7

2017.08.27 - GNU nano 2.8.7 "Fragrance" fixes a lockup when tabs are
wider than the screen, makes indenting + unindenting
more predictable by retaining relative indentations,
allows pasting (^U) at a prompt, allows triple quotes
in Python to not be followed by a character, does not
scroll three pages on a roll of the mouse wheel, binds
Alt+Up and Alt+Down to findprevious and findnext, and
fixes some hard-to-describe issues with softwrapping
and boundary-crossing tabs.  Enjoy.

(wiedi)