Macros starting with `u' in osfmk/vm

• UPDATE_FIRST_FREE osfmk/vm/vm_map.c:478
• upl_lock osfmk/vm/vm_pageout.h:118
• upl_lock_init osfmk/vm/vm_pageout.h:117
• upl_unlock osfmk/vm/vm_pageout.h:119