Cleanup of a number of uninitialized variable issues flagged by

the compiler.  Some are obscure functions (plot verstatec hasn't
been used in years) but others (like SPICE distributed junctions)
are potentially significant sources of unexpected crashes on
systems that don't zero uninitialized memory.

plot/plotRutils.c

@@ -196,6 +196,7 @@ PlotFreeRaster(raster)
 				 * have been created with PlotNewRaster.
 				 */
 {
+    if (raster == NULL) return;
     freeMagic((char *) raster->ras_bits);
     freeMagic((char *) raster);
 }