Fixup warnings

Author: diwic

src/ctl_int.rs

@@ -24,7 +24,7 @@ const ELEM_ID_SIZE: usize = 64;
 pub struct DeviceIter<'a>(&'a Ctl, c_int);
 
 impl<'a> DeviceIter<'a>{
-    pub fn new(ctl: &'a Ctl) -> DeviceIter {
+    pub fn new(ctl: &'a Ctl) -> DeviceIter<'a> {
         DeviceIter(ctl, -1)
     }
 }

src/hctl.rs

@@ -25,6 +25,14 @@
 //! }
 //! ```
 
+#![allow(dead_code)]
+/* There is a "field is never read" warning for the ElemIter struct. We still need to hold on
+   to the HCtl pointer somehow; to guarantee that the HCtl does not go out of scope while we use
+   ElemIter, which would make the snd_hctl_elem_t pointer invalid. Hence the decision to allow dead code here.
+   I suppose there is a better solution for this but I'm not sure how.
+*/
+
+
 use crate::{alsa, Card};
 use std::ffi::{CStr, CString};
 use super::error::*;