Feature-gate batch inversion and compression on alloc

src/field.rs

@@ -184,6 +184,7 @@ impl FieldElement {
     ///
     /// This function is most efficient when the batch size (slice
     /// length) is a power of 2.
+    #[cfg(any(feature = "alloc", feature = "std"))]
     pub fn batch_invert(inputs: &mut [FieldElement]) {
         // First, compute the product of all inputs using a product
         // tree:

src/ristretto.rs

@@ -667,6 +667,7 @@ impl RistrettoPoint {
     }
 
     /// Double-and-compress a batch of points.
+    #[cfg(any(feature = "alloc", feature = "std"))]
     pub fn double_and_compress_batch<'a, I>(points: I) -> Vec<CompressedRistretto> 
         where I: IntoIterator<Item = &'a RistrettoPoint>
     {