Added ToString() to the macro-based declarations for better debug output.

src/Bridge/Preprocessor.cs

@@ -28,6 +28,11 @@
             //return visitor.VisitMacroExpansion(this);
             return default(T);
         }
+
+        public override string ToString()
+        {
+            return Text;
+        }
     }
 
     /// <summary>
@@ -46,5 +51,10 @@
         {
             return visitor.VisitMacroDefinition(this);
         }
+
+        public override string ToString()
+        {
+            return Expression;
+        }
     }
 }