Defines starting with `z' in osfmk/kern

• Z_COLLECT osfmk/kern/zalloc.h:171
• Z_EXHAUST osfmk/kern/zalloc.h:170
• Z_EXPAND osfmk/kern/zalloc.h:172
• Z_FOREIGN osfmk/kern/zalloc.h:173
• ZONE_NULL osfmk/kern/kern_types.h:91