Added impls of `Saturating…` for `i128` and `u128`

src/ops/saturating.rs

@@ -26,3 +26,5 @@ macro_rules! saturating_impl {
 }
 
 saturating_impl!(Saturating for isize usize i8 u8 i16 u16 i32 u32 i64 u64);
+#[cfg(feature = "i128")]
+saturating_impl!(Saturating for i128 u128);