relative locktime: use From/TryFrom to convert between relative locktimes and Sequence

bitcoin/src/blockdata/locktime/relative.rs

@@ -6,7 +6,7 @@
 //! whether bit 22 of the `u32` consensus value is set.
 //!
 
-use core::{cmp, fmt};
+use core::{cmp, convert, fmt};
 
 #[cfg(all(test, mutate))]
 use mutagen::mutate;
@@ -307,6 +307,17 @@ impl fmt::Display for LockTime {
     }
 }
 
+impl convert::TryFrom<Sequence> for LockTime {
+    type Error = DisabledLockTimeError;
+    fn try_from(seq: Sequence) -> Result<LockTime, DisabledLockTimeError> {
+        LockTime::from_sequence(seq)
+    }
+}
+
+impl From<LockTime> for Sequence {
+    fn from(lt: LockTime) -> Sequence { lt.to_sequence() }
+}
+
 /// Error returned when a sequence number is parsed as a lock time, but its
 /// "disable" flag is set.
 #[derive(Debug, Clone, Eq, PartialEq)]