Fix reference error

Author: Phlosioneer

src/libstd/sys/windows/os.rs

@@ -197,7 +197,7 @@ impl<'a> Iterator for SplitPaths<'a> {
         // There will be at most N + 1 entries, where N is the number of
         // remaining semicolons.
         let data = self.data.clone();
-        let semicolons = data.filter(|b| b == (';' as u16)).count();
+        let semicolons = data.filter(|&b| b == (';' as u16)).count();
 
         (0, Some(semicolons + 1))
     }