Fixed C++ 98 build

glm/detail/setup.hpp

@@ -710,6 +710,12 @@ namespace detail
 		typedef unsigned char type;
 	};
 
+	template<>
+	struct make_unsigned<signed char>
+	{
+		typedef unsigned char type;
+	};
+
 	template<>
 	struct make_unsigned<short>
 	{