* Perform all iOS logging through ASL
As of iOS 10, ASL is deprecated and replaced with os_log. ASL calls
continue to result in logging but as of iOS 10.3, only ASL_LOG_NOTICE
level and above are logged.
This change partially reverts 2937f06a15cecf5e9398334617ca156316dae52b,
adding back stdout and stderr redirection, which resulted in loss of
some direct writes to stdout that were necessary for debugging.
This change replaces the direct use of syslog with ASL on iOS, which
Apple has stated will continue to log on iOS >= 10. This eliminates the
need for the previous fwd-declaration of syslog.
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