File descriptor not closed in TimerFd

[crdumoul]

As specified in https://man7.org/linux/man-pages/man2/timerfd_create.2.html the file descriptor for a timerfd should be closed when it is no longer required. In nix::sys::timerfd::TimerFd there is no Drop implementation and the file descriptor is not automatically closed. This leads to a file descriptor leak.

The TimerFd struct either needs to properly own the file descriptor and close it when it's dropped, or make it explicit through documentation that the user of TimerFd needs to close the file descriptor themselves.

[asomers]

Good catch! Would you be willing to submit a PR to fix it?

[crdumoul]

I'll do that shortly.