@ZOS: Improve "Access a private function" error message

[votan]

@Chip: Any chance that the error message "attempt to access a private function '...' from insecure code" could include more information why the exception is raised?
The call-stack does not really help most times.

If this could cause some slowdown due to overhead, you may add a switch in the UserSettings.txt. So that one can enable it to track down the problem.

Or does such a switch exists already?

Any other advices?