Provide rvalue cast operator for ResultValue

Allows objects returned as ResultValue (instead of
ResultValueType::type) to be moved without requiring
additional casting or explicit use of ResultValue::value.

Resolves #589

vulkan/vulkan.hpp

@@ -15864,6 +15864,11 @@ namespace VULKAN_HPP_NAMESPACE
     {
       return value;
     }
+
+    operator T &&() && VULKAN_HPP_NOEXCEPT
+    {
+      return std::move( value );
+    }
 #endif
   };