hardcopy plotting does NOT call fuser

It isn't obviously needed (10 years ago I saw something that maybe said this was
needed). And currently this generates lots of console chatter about "permission
denied" accessing stuff completely unrelated to the plotting

new release

feedgnuplot Debian release 1.63-1

I explicitly ignore all lines that have '-' values

These may come from vnl-filter -p "dx=diff(x)" ... output. For instance, this
plot is broken before this patch:

  (echo '# x'; seq 5) | vnl-filter --noskipempty -p 'd=diff(x)' \
  | feedgnuplot --lines

feedgnuplot Debian release 1.62-1

changelog bump

changelog bump

version bump

feedgnuplot Debian release 1.60-1

version bump