Work-around for "black block symbol" syndrome.

- scripts/gitsch2ppm (ps2ppm): convert "rectfill" to "rectstroke", to
  prevent colored background in schematic symbols from blackening the
  entire symbol in black and white plot

scripts/gitsch2ppm

@@ -26,6 +26,7 @@ ps2ppm()
     ( cat <<EOF
 %!PS-Adobe-3.0
 /setlinewidth { $LINEWIDTH 2 copy lt { exch } if pop setlinewidth } bind def
+/rectfill { rectstroke } bind def
 EOF
     sed 1d <"$1"; ) |
 	gs -sDEVICE=ppmraw -sOutputFile=- -g$IRES -r$res \