Remove len and is_empty from impl_array_newtype macros

An array in Rust has no concept of length, it is a fixed size data type.
Equally an array cannot be "empty", again since it is a fixed size data
type. These are methods/concepts seen in slices and vectors.

Remove the `len` and `is_empty` methods.

secp256k1-sys/src/macros.rs

@@ -19,16 +19,6 @@ macro_rules! impl_array_newtype {
     ($thing:ident, $ty:ty, $len:expr) => {
         impl Copy for $thing {}
 
-        impl $thing {
-            /// Returns the length of the object as an array.
-            #[inline]
-            pub fn len(&self) -> usize { $len }
-
-            /// Returns whether the object as an array is empty.
-            #[inline]
-            pub fn is_empty(&self) -> bool { false }
-        }
-
         impl AsRef<[$ty; $len]> for $thing {
             #[inline]
             /// Gets a reference to the underlying array

src/macros.rs

@@ -19,16 +19,6 @@ macro_rules! impl_array_newtype {
     ($thing:ident, $ty:ty, $len:expr) => {
         impl Copy for $thing {}
 
-        impl $thing {
-            /// Returns the length of the object as an array.
-            #[inline]
-            pub fn len(&self) -> usize { $len }
-
-            /// Returns whether the object as an array is empty.
-            #[inline]
-            pub fn is_empty(&self) -> bool { false }
-        }
-
         impl AsRef<[$ty; $len]> for $thing {
             #[inline]
             /// Gets a reference to the underlying array