Fix, the newer MinGW gives warnings for the default visibility, if it's not applicable.
Fix, the newer MinGW gives warnings for the default visibility, if it's not applicable.

That gives many warnings for each class of Nuitka helpers and generated code, so we don't
provide such a default anymore.

kayhayen/Nuitka,tempbottle/Nuitka,wfxiang08/Nuitka,kayhayen/Nuitka,kayhayen/Nuitka,wfxiang08/Nuitka,kayhayen/Nuitka,wfxiang08/Nuitka,tempbottle/Nuitka,tempbottle/Nuitka,wfxiang08/Nuitka,tempbottle/Nuitka