Add vo-amrwbenc library package.

With some changes to ffmpeg build file, this enables ffmpeg to perform
AMR-WB encoding.

pkgs/development/libraries/vo-amrwbenc/default.nix

@@ -0,0 +1,21 @@
+{ stdenv, fetchurl, autoreconfHook }:
+
+let
+    version = "0.1.3";
+in
+stdenv.mkDerivation {
+  name = "vo-amrwbenc-${version}";
+  version = "0.1.3";
+  buildInputs = [ autoreconfHook ];
+  src = fetchurl {
+    url = "https://github.com/mstorsjo/vo-amrwbenc/archive/v${version}.tar.gz";
+    sha256 = "85c79997ba7ddb9c95b5ddbe9ea032e27595390f3cbd686ed46a69e485cc053c";
+  };
+
+  meta = {
+    homepage = "http://sourceforge.net/projects/opencore-amr/";
+    description = "VisualOn Adaptive Multi Rate Wideband (AMR-WB) encoder";
+    license = "stdenv.lib.licenses.apache";
+    maintainers = [ stdenv.lib.maintainers.esteth ];
+  };
+}

pkgs/top-level/all-packages.nix

@@ -5222,6 +5222,8 @@ with pkgs;
 
   vncrec = callPackage ../tools/video/vncrec { };
 
+  vo-amrwbenc = callPackage ../development/libraries/vo-amrwbenc { };
+
   vobcopy = callPackage ../tools/cd-dvd/vobcopy { };
 
   vobsub2srt = callPackage ../tools/cd-dvd/vobsub2srt { };