Is the Mach API publicly available to use in iOS apps?

Is the Mach API (mach/mach.h, mach/ma开发者_运维知识库ch_time.h, etc.) OK to use in iOS apps that are intended for the App Store, or will they get your app rejected?

I've been told that they are part of the 'SPI' (System Programming Interface) and therefore inaccessible.

To provide one answer to my question, I know of one person who is using mach_wait_until in an iOS app that is in the app store. He has confirmed that apple had no problems with him using it.