Defines starting with `d' in vm

• DDB_ALLOC vm/device_pager.c:62
• DDB_FAIL vm/device_pager.c:63
• DDB_FOLLOW vm/device_pager.c:60
• DDB_INIT vm/device_pager.c:61
• DEFAULT_PAGE_SIZE vm/vm_param.h:85
• _DEVICE_PAGER_ vm/device_pager.h:42
• DEV_PAGER_NULL vm/device_pager.h:57