Don't output HTML anchors for non-unique labels

We're generating names that nothing links to.  The names aren't
guaranteed unique, so they're of dubious value anyway.

Also, fixed the Atari 2600 visualizer script filename in sys defs.

SourceGen/Exporter.cs

@@ -602,9 +602,16 @@ namespace SourceGen {
                         line.LineType == LineListGen.Line.Type.Data ||
                         line.LineType == LineListGen.Line.Type.EquDirective) &&
                     !string.IsNullOrEmpty(parts.Label)) {
+                if (parts.Label.StartsWith(mFormatter.NonUniqueLabelPrefix)) {
+                    // TODO(someday): handle non-unique labels.  ':' is valid in HTML anchors,
+                    // so we can use that to distinguish them from other labels, but we still
+                    // need to ensure that the label is unique and all references point to the
+                    // correct instance.  We can't get that from the Parts list.
+                } else {
                     anchorLabel = "<a name=\"" + LABEL_LINK_PREFIX + parts.Label +
                         "\">" + parts.Label + "</a>";
                 }
+            }
 
             // If needed, create an HTML link for the operand field.
             string linkOperand = null;

SourceGen/RuntimeData/SystemDefs.json

@@ -137,7 +137,7 @@
         "RT:Atari/2600.sym65"
       ],
       "ExtensionScripts" : [
-        "RT:Atari/VisAtari2600.cs"
+        "RT:Atari/Vis2600.cs"
       ],
       "Parameters" : {
         "load-address":"0xf000"