fold --spaces-have-priority-over-width wishlist.

[Dan Jacobson]

fold has:
`-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.
Could add a switch to make --spaces have priority over width,
guaranteeing never a truncated word, while still enjoying the benefits
of --width.