Adding an implementation and some basic tests for timerfd.

Removed support for timerfd on Android as it seems to have been deprecated? See https://android.googlesource.com/platform/development/+/73a5a3b/ndk/platforms/android-20/include/sys/timerfd.h or https://github.com/rust-lang/libc/issues/1589

Removed the public status of `TimerSpec`, as it should not be exposed to the user.

Implemented `FromRawFd` for `TimerFd` as it already implements `AsRawFd`.

Addressed comments from the latest code review:
  - Removed upper bound assertions on timer expirations in tests.
  - Made the main example runnable and added code to show how to wait for the timer.
  - Refactored `ClockId` to use `libc_enum`.
  - Added comments for all public parts of the module.
  - Wrapped to 80 cols.
  - Changed the size of the buffer in the tests to the minimum required.

* Ran rustfmt.
* Added a `From` implementation for `libc::timespec` -> `TimeSpec`.
* Reworked the example with the new changes and changed the timer from 5 to 1 second.
* Added a constructor for a 0-initialized `TimerSpec`.
* Added a new method to get the timer configured expiration (based on timerfd_gettime).
* Added an helper method to unset the expiration of the timer.
* Added a `wait` method to actually read from the timer.
* Renamed `settime` into just `set`.
* Refactored the tests and added a new one that tests both the `unset` and the `get` method.

Modified CHANGELOG.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/sys/time.rs b/src/sys/time.rs
index 51baa9e1..973a3526 100644
--- a/src/sys/time.rs
+++ b/src/sys/time.rs
@@ -60,6 +60,11 @@ const TS_MAX_SECONDS: i64 = ::std::isize::MAX as i64;
 
 const TS_MIN_SECONDS: i64 = -TS_MAX_SECONDS;
 
+impl From<timespec> for TimeSpec {
+    fn from(ts: timespec) -> Self {
+        Self(ts)
+    }
+}
 
 impl AsRef<timespec> for TimeSpec {
     fn as_ref(&self) -> &timespec {