Local variables mostly work

Variables are now handled properly end-to-end, except for label
uniquification.  So cc65 and ACME can't yet handle a file that
redefines a local variable.

This required a bunch of plumbing, but I think it came out okay.

SourceGen/MainController.cs

@@ -435,6 +435,7 @@ namespace SourceGen {
             mFormatterConfig = new Formatter.FormatConfig();
             AsmGen.GenCommon.ConfigureFormatterFromSettings(AppSettings.Global,
                 ref mFormatterConfig);
+            //mFormatterConfig.mLocalVariableLablePrefix = "\u00a4";  // CURRENCY SIGN
             mFormatterConfig.mEndOfLineCommentDelimiter = ";";
             mFormatterConfig.mFullLineCommentDelimiterBase = ";";
             mFormatterConfig.mBoxLineCommentDelimiter = string.Empty;