Constant nc::types::TFD_TIMER_ABSTIME

pub const TFD_TIMER_ABSTIME: i32 = 1 << 0; // 1i32

CAREFUL: Check include/asm-generic/fcntl.h when defining new flags, since they might collide with O_* ones. We want to re-use O_* flags that couldn’t possibly have a meaning from eventfd, in order to leave a free define-space for shared O_* flags.

Also make sure to update the masks in include/linux/timerfd.h when adding new flags.