Defines starting with `u' in osfmk/kern

• ULOCK_FREE osfmk/kern/sync_lock.h:81
• ULOCK_HELD osfmk/kern/sync_lock.h:82
• ULOCK_NULL osfmk/kern/sync_lock.h:79
• USAGE_THRESHOLD osfmk/kern/priority.c:85
• USIMPLE_LOCK_NULL osfmk/kern/simple_lock_types.h:196
• USLOCK_CHECKED osfmk/kern/lock.c:424
• USLOCK_DEBUG osfmk/kern/simple_lock_types.h:255
• USLOCK_DEBUG_DATA osfmk/kern/simple_lock_types.h:151
• USLOCK_INIT osfmk/kern/lock.c:426
• USLOCK_INITIALIZED osfmk/kern/lock.c:427
• USLOCK_STACK_DEPTH osfmk/kern/lock.c:752
• USLOCK_TAG osfmk/kern/simple_lock_types.h:191
• USLOCK_TAKEN osfmk/kern/lock.c:425