pdb -> rdi: correctly convert negative enumerate numerics; move enum value visualization into complex string-iterator visualization path, rather than hacking it into the simply-typed eval path (we want to generate a new task for the numeric value itself); handle negative enums correctly

src/mule/mule_main.cpp

@@ -217,6 +217,7 @@ raddbg_type_view(PackedF16,
 
 enum Kind
 {
+  Kind_Negative = -1,
   Kind_None,
   Kind_First,
   Kind_Second,