This change implements NOTE_MONOTONIC flag for EVFILT_TIMER, which specifies that the data field contains absolute time to fire the event.
To make this useful, data member of the struct kevent must be extended to 64bit. Using the opportunity, I also increased size of ident to 64bit and added ext members. This changes struct kevent almost to Apple struct kevent64, except I did not changed type of udata, the later would cause serious API incompatibilities.
Unlike Apple kevent64, symbol versioning allows us to claim ABI compatibility and still name the new syscall kevent(2). Compat shims are provided for both host native and compat32.