Fields
- Head: mach_msg_header_t
- msgh_body: mach_msg_body_t
- old_handlers: [32] mach_msg_port_descriptor_t
- NDR: NDR_record_t
- masksCnt: mach_msg_type_number_t
- masks: [32] exception_mask_t
- old_behaviors: [32] exception_behavior_t
- old_flavors: [32] thread_state_flavor_t