Add "close" to io-lifetimes feature set

[phi-gamma]

Without this feature enabled the eventfd test crashes on my box:

---- eventfd::test_eventfd stdout ----
thread 'eventfd::test_eventfd' panicked at 'internal error: entered unreachable code: drop called without the "close" feature in io-lifetimes', /root/.cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/io-lifetimes-1.0.0-rc1/src/types.rs:763:13
stack backtrace:
   0: rust_begin_unwind
             at /datastore/rpmbuild/BUILD/rustc-1.57.0-src/library/std/src/panicking.rs:517:5
   1: core::panicking::panic_fmt
             at /datastore/rpmbuild/BUILD/rustc-1.57.0-src/library/core/src/panicking.rs:100:14
   2: <io_lifetimes::types::OwnedFd as core::ops::drop::Drop>::drop
             at /root/.cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/io-lifetimes-1.0.0-rc1/src/types.rs:763:13
   3: core::ptr::drop_in_place<io_lifetimes::types::OwnedFd>
             at /datastore/rpmbuild/BUILD/rustc-1.57.0-src/library/core/src/ptr/mod.rs:188:1
   4: io::eventfd::test_eventfd
             at ./tests/io/eventfd.rs:24:1
   5: io::eventfd::test_eventfd::{{closure}}
             at ./tests/io/eventfd.rs:3:1
   6: core::ops::function::FnOnce::call_once
             at /datastore/rpmbuild/BUILD/rustc-1.57.0-src/library/core/src/ops/function.rs:227:5
   7: core::ops::function::FnOnce::call_once
             at /datastore/rpmbuild/BUILD/rustc-1.57.0-src/library/core/src/ops/function.rs:227:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[sunfishcode]

Thanks!