Be more relaxed with c_void

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "cpal"
-version = "0.2.10"
+version = "0.2.11"
 authors = ["Pierre Krieger <pierre.krieger1708@gmail.com>"]
 description = "Cross-platform audio playing library in pure Rust."
 repository = "https://github.com/tomaka/cpal"

src/alsa/mod.rs

@@ -353,7 +353,7 @@ impl<'a, T> Buffer<'a, T> {
         unsafe {
             loop {
                 let result = alsa::snd_pcm_writei(*channel,
-                                                  self.buffer.as_ptr() as *const libc::c_void,
+                                                  self.buffer.as_ptr() as *const _,
                                                   to_write);
 
                 if result == -32 {