Assume has_reverse_bits

Author: cuviper

build.rs

@@ -3,7 +3,6 @@ use std::env;
 fn main() {
     let ac = autocfg::new();
 
-    ac.emit_expression_cfg("1u32.reverse_bits()", "has_reverse_bits");
     ac.emit_expression_cfg("1u32.trailing_ones()", "has_leading_trailing_ones");
     ac.emit_expression_cfg("1u32.div_euclid(1u32)", "has_div_euclid");
 

src/int.rs

@@ -461,7 +461,6 @@ macro_rules! prim_int_impl {
                 <$T>::swap_bytes(self)
             }
 
-            #[cfg(has_reverse_bits)]
             #[inline]
             fn reverse_bits(self) -> Self {
                 <$T>::reverse_bits(self)