Added a second version of the rm_watch function to deal with android.

src/sys/inotify.rs

@@ -152,12 +152,20 @@ impl Inotify {
     /// Returns an EINVAL error if the watch descriptor is invalid.
     ///
     /// For more information see, [inotify_rm_watch(2)](http://man7.org/linux/man-pages/man2/inotify_rm_watch.2.html).
+    #[cfg(target_os = "linux")]
     pub fn rm_watch(&self, wd: WatchDescriptor) -> Result<()> {
         let res = unsafe { libc::inotify_rm_watch(self.fd, wd.wd) };
 
         Errno::result(res).map(drop)
     }
 
+    #[cfg(target_os = "android")]
+    pub fn rm_watch(&self, wd: WatchDescriptor) -> Result<()> {
+        let res = unsafe { libc::inotify_rm_watch(self.fd, wd.wd as u32) };
+
+        Errno::result(res).map(drop)
+    }
+
     /// Reads a collection of events from the inotify file descriptor. This call
     /// can either be blocking or non blocking depending on whether IN_NONBLOCK
     /// was set at initialization.