From Marco Jez, warning fixes.

include/osgIntrospection/Comparator

@@ -25,6 +25,7 @@ namespace osgIntrospection
 	{
 		virtual bool isEqualTo(const Value& l, const Value& r) const = 0;
 		virtual bool isLessThanOrEqualTo(const Value& l, const Value& r) const = 0;
+		virtual ~Comparator() {}
 	};
 	
 	template<typename T>
@@ -41,6 +42,8 @@ namespace osgIntrospection
 		{
 			return variant_cast<const T &>(l) <= variant_cast<const T &>(r);
 		}
+		
+		virtual ~TotalOrderComparator() {}
 	};
 	
 	template<typename T>
@@ -55,6 +58,8 @@ namespace osgIntrospection
 		{
 			throw ComparisonOperatorNotSupportedException(typeid(T), "less than or equal to");
 		}
+		
+		virtual ~PartialOrderComparator() {}
 	};
 
 }