Auto merge of #13697 - mmatyas:android_cvoid, r=emilio

Fix missing `c_void` error when building for Android

<!-- Please describe your changes on the following line: -->
Including `c_void` is also required on Android, because of https://github.com/mmatyas/servo/blob/master/ports/glutin/window.rs#L170

(This is a fix for #13154)

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/13697)
<!-- Reviewable:end -->

ports/glutin/window.rs

@@ -32,7 +32,6 @@ use std::cell::{Cell, RefCell};
 use std::ffi::CString;
 #[cfg(any(target_os = "linux", target_os = "macos"))]
 use std::mem;
-#[cfg(not(target_os = "android"))]
 use std::os::raw::c_void;
 use std::ptr;
 use std::rc::Rc;