Use task_t, thread_t, and exception_handler_t uniformly

util/mach/mach_extensions.h

Index: util/mach/mach_extensions.h
diff --git a/util/mach/mach_extensions.h b/util/mach/mach_extensions.h
index f9d04b71c10cecf97960f44117bc3babc169ea86..14a2862fc645e456df3d7461891ce024f261f34b 100644
--- a/util/mach/mach_extensions.h
+++ b/util/mach/mach_extensions.h
@@ -65,7 +65,7 @@ const exception_type_t kMachExceptionSimulated = 'CPsx';
 //!     count. The returned port must not be deallocated by
 //!     `mach_port_deallocate()`. The returned value is valid as long as the
 //!     thread continues to exist as a `pthread_t`.
-mach_port_t MachThreadSelf();
+thread_t MachThreadSelf();
 
 //! \brief The value for `EXC_MASK_ALL` appropriate for the operating system at
 //!     run time.