apple: include proper mach primatives

Fixes implicit declaration warning for 'mach_task_self'. This change
is an update to Change I9991dedd1ccfddc092eca86705ecbc3b764b799d,
which fixed this issue for the decoder but not the encoder.

Change-Id: I9df033e81f9520c4f975b7a7cf6c643d12e87c96