Add override BitSet.ToString

runtime/CSharp/Antlr4.Runtime/Sharpen/BitSet.cs

@@ -280,5 +280,22 @@ namespace Sharpen
 
             return result.GetHashCode();
         }
+
+        public override string ToString()
+        {
+            StringBuilder builder = new StringBuilder();
+            builder.Append('{');
+
+            for (int i = NextSetBit(0); i >= 0; i = NextSetBit(i + 1))
+            {
+                if (builder.Length > 1)
+                    builder.Append(", ");
+
+                builder.Append(i);
+            }
+
+            builder.Append('}');
+            return builder.ToString();
+        }
     }
 }