Change syntax - the previous one didn't actually work

Author: Aaron1011

src/macros.rs

@@ -152,7 +152,7 @@ cfg_if! {
     if #[cfg(feature = "extern-const-fn")] {
         #[allow(unused_macros)]
         macro_rules! f {
-            ($(pub fn $i:ident($($arg:ident: $argty:ty),*) $($constness:ident)* -> $ret:ty  {
+            ($(pub $({$constness:ident})* fn $i:ident($($arg:ident: $argty:ty),*) -> $ret:ty {
                 $($body:stmt);*
             })*) => ($(
                 #[inline]
@@ -163,7 +163,7 @@ cfg_if! {
         }
     } else {
         macro_rules! f {
-            ($(pub fn $i:ident($($arg:ident: $argty:ty),*) $($constness:ident)* -> $ret:ty  {
+            ($(pub $({$constness:ident})* fn $i:ident($($arg:ident: $argty:ty),*) -> $ret:ty {
                 $($body:stmt);*
             })*) => ($(
                 #[inline]

src/unix/linux_like/mod.rs

@@ -1182,7 +1182,7 @@ f! {
         cmsg.offset(1) as *mut ::c_uchar
     }
 
-    pub fn CMSG_SPACE(length: ::c_uint) const -> ::c_uint {
+    pub {const} fn CMSG_SPACE(length: ::c_uint) -> ::c_uint {
         (CMSG_ALIGN(length as usize) + CMSG_ALIGN(::mem::size_of::<cmsghdr>()))
             as ::c_uint
     }