Correct the value of FAN_MARK_IGNORE

[severen]

This PR aligns the value of FAN_MARK_IGNORE in libc with that in uapi/linux/fanotify.h.

Previously, it was incorrectly set to the value of FAN_MARK_MOUNT, which can cause subtle but catastrophic bugs when one tries to mark a file as ignored.

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[severen]

I've also gone through and compared all of the other fanotify constants with those in uapi/linux/fanotify.h to see if I could spot any other mismatches, but it looks like everything else is correct.