a52dec: Add patches from Handbrake project

this project hasn't been updated in 10 years, so adding patches that
don't break the API should be ok.

Patches:
- A00: Make a52-state-t public
- A01: Make it thread-safe (changing internal API by adding state
objects)
- A02: Quell common error
- A03: Fix for automake vs autoconf

pkgs/development/libraries/a52dec/default.nix

@@ -1,7 +1,7 @@
 {stdenv, fetchurl}:
 
 stdenv.mkDerivation rec {
-  name = "a52dec-0.7.4";
+  name = "a52dec-0.7.4p4";
   
   src = fetchurl {
     url = "${meta.homepage}/files/a52dec-0.7.4.tar.gz";
@@ -10,6 +10,14 @@ stdenv.mkDerivation rec {
 
   NIX_CFLAGS_COMPILE = "-fpic";
 
+  # From Handbrake
+  patches = [
+    ./A00-a52-state-t-public.patch
+    ./A01-thread-safe.patch
+    ./A02-imdct-shutup.patch
+    ./A03-automake.patch
+  ];
+
   meta = {
     description = "ATSC A/52 stream decoder";
     homepage = http://liba52.sourceforge.net/;