bug#25199: fold -s --dont-fracture-non-whitespace

[積丹尼 Dan Jacobson]

(info "(coreutils) fold invocation")

‘-s’
‘--spaces’
     Break at word boundaries: the line is broken after the last blank
     before the maximum line length.  If the line contains no such
     blanks, the line is broken at the maximum line length as usual.

Add:
     unless --dont-fracture-non-whitespace is given, in which case such lines
     are left unscathed.

And implement it, as it would be pretty hard for the user to do on his
own, and it would be the only way to yes break at spaces, but to no,
don't axe words etc. in half.

fold (GNU coreutils) 8.26