gstreamer: 1.8.0 -> 1.8.1 (bugfixes)

Release notes:
https://gstreamer.freedesktop.org/releases/gstreamer/1.8.1.html

Tested with nox-review; this change does not introduce build breakage.

pkgs/development/libraries/gstreamer/libav/default.nix

@@ -9,7 +9,7 @@
 assert withSystemLibav -> libav != null;
 
 stdenv.mkDerivation rec {
-  name = "gst-libav-1.8.0";
+  name = "gst-libav-1.8.1";
 
   meta = {
     homepage = "http://gstreamer.freedesktop.org";
@@ -19,7 +19,7 @@ stdenv.mkDerivation rec {
 
   src = fetchurl {
     url = "${meta.homepage}/src/gst-libav/${name}.tar.xz";
-    sha256 = "0719njp8aarhvn038pijq6dmsnli0zlg146hyfs3rsdffs4f472s";
+    sha256 = "0cw9nc0079vmdp5r8hrrmglb1bzvsxy298j6yg25l6skqc493924";
   };
 
   outputs = [ "dev" "out" ];