util/frame/video: implement DerefMut

src/util/frame/video.rs

@@ -1,6 +1,6 @@
 use libc::c_int;
 use std::mem;
-use std::ops::Deref;
+use std::ops::{Deref, DerefMut};
 
 use ffi::*;
 use ::{Rational, Picture};
@@ -189,6 +189,12 @@ impl Deref for Video {
 	}
 }
 
+impl DerefMut for Video {
+	fn deref_mut(&mut self) -> &mut Frame {
+		&mut self.0
+	}
+}
+
 impl Clone for Video {
 	fn clone(&self) -> Self {
 		Video(self.0.clone())