api: gate 'into_owned' on 'alloc' feature

We did this for the forward case but apparently didn't follow through
for the reverse case.

We also simplify the endianness diagnostic test.

src/memmem/mod.rs

@@ -336,7 +336,7 @@ impl<'h, 'n> FindRevIter<'h, 'n> {
     /// this copies the needle.
     ///
     /// This is only available when the `std` feature is enabled.
-    #[cfg(feature = "std")]
+    #[cfg(feature = "alloc")]
     #[inline]
     pub fn into_owned(self) -> FindRevIter<'h, 'static> {
         FindRevIter {
@@ -606,7 +606,7 @@ impl<'n> FinderRev<'n> {
     /// this copies the needle.
     ///
     /// This is only available when the `std` feature is enabled.
-    #[cfg(feature = "std")]
+    #[cfg(feature = "alloc")]
     #[inline]
     pub fn into_owned(self) -> FinderRev<'static> {
         FinderRev {

src/tests/mod.rs

@@ -6,14 +6,10 @@ pub(crate) mod substring;
 
 // For debugging, particularly in CI, print out the byte order of the current
 // target.
-#[cfg(all(feature = "std", target_endian = "little"))]
 #[test]
 fn byte_order() {
+    #[cfg(target_endian = "little")]
     std::eprintln!("LITTLE ENDIAN");
-}
-
-#[cfg(all(feature = "std", target_endian = "big"))]
-#[test]
-fn byte_order() {
+    #[cfg(target_endian = "big")]
     std::eprintln!("BIG ENDIAN");
 }