Adding avxsynth.

To add it, I also add ffms and log4cpp.

pkgs/development/libraries/log4cpp/default.nix

@@ -0,0 +1,16 @@
+{ stdenv, fetchurl }:
+
+stdenv.mkDerivation rec {
+  name = "log4cpp-1.1";
+  
+  src = fetchurl {
+    url = "mirror://sourceforge/log4cpp/${name}.tar.gz";
+    sha256 = "1d386ws9v6f9bxma4dh5m6nzr4k2rv5q96xl5bp5synlmghd2ny2";
+  };
+
+  meta = {
+    homepage = http://log4cpp.sourceforge.net/;
+    description = "A logging framework for C++ patterned after Apache log4j";
+    license = "LGPLv2.1+";
+  };
+}