Issue Description:

The os_log function in the SDK overlay has an overload defined that puts the type argument first. But for some reason this overload has an @available attribute that marks it as macOS 10.14, iOS 12.0, etc even though os_log is available in macOS 10.12, iOS 10.0, etc. The overload may be new in the macOS 10.14, iOS 12, etc SDK, but it's purely an artifact of the SDK overlay and the underlying functions it calls exist in macOS 10.12, iOS 10, etc (in fact, its implementation is literally identical to the original function). There's no reason at all for this overload to have an availability that differs from the original function.