Add missing attributes

Author: Aaron1011

src/macros.rs

@@ -165,6 +165,7 @@ cfg_if! {
             )*)
         }
 
+        #[allow(unused_macros)]
         macro_rules! const_fn {
             ($($({$constness:ident})* fn $i:ident(
                         $($arg:ident: $argty:ty),*
@@ -195,6 +196,7 @@ cfg_if! {
             )*)
         }
 
+        #[allow(unused_macros)]
         macro_rules! const_fn {
             ($($({$constness:ident})* fn $i:ident(
                         $($arg:ident: $argty:ty),*