Use '*' for full-line Merlin comments

While it's okay to use ';', the classic Merlin editor will treat it
as an end-of-line comment and shove the entire thing off to the right
side of the screen.

This adds a configuration item to the app settings, with a default
value of ';'.

SourceGen/MainController.cs

@@ -493,7 +493,6 @@ namespace SourceGen {
             AsmGen.GenCommon.ConfigureFormatterFromSettings(AppSettings.Global,
                 ref mFormatterConfig);
             mFormatterConfig.EndOfLineCommentDelimiter = ";";
-            mFormatterConfig.FullLineCommentDelimiterBase = ";";
             mFormatterConfig.BoxLineCommentDelimiter = string.Empty;
 
             mFormatterConfig.NonUniqueLabelPrefix =