Misc macOS code cleanups and minor fixes

This contains mostly code cleanup and changes to fast iteration (for … in loops).

Additionally a quite important fix for an assertion that could be caused by invalid index to count comparison, fixed by macosx: Fix off-by-one in reload logic

@fkuehne Some clarifications about the logic in reloadDataForNotification would be appreciated as I am having a bit trouble to understand what is supposed to happen there.