wavegain: Add package.

This adds wavegain which is a normalizer for WAV audio files.

pkgs/applications/audio/wavegain/default.nix

···
+{ stdenv, fetchgit }:
+
+stdenv.mkDerivation {
+  name = "wavegain-1.3.1";
+  src = fetchgit {
+    url = "https://github.com/MestreLion/wavegain.git";
+    sha256 = "1h886xijc9d7h4p6qx12c6kgwmp6s1bdycnyylkayfncczzlbi24";
+  };
+
+  installPhase = ''
+    strip -s wavegain
+    install -vD wavegain "$out/bin/wavegain"
+  '';
+
+  meta = {
+    description = "ReplayGain for wave files";
+    homepage = https://github.com/MestreLion/wavegain;
+    license = stdenv.lib.licenses.lgpl21;
+    platforms = stdenv.lib.platforms.linux;
+    maintainers = [ stdenv.lib.maintainers.devhell ];
+  };
+}

pkgs/top-level/all-packages.nix

···
 
   VisualBoyAdvance = callPackage ../misc/emulators/VisualBoyAdvance { };
 
+  wavegain = callPackage ../applications/audio/wavegain { };
+
   # Wine defaults to a mixed 64 / 32 build on x86_64 and to pure 32 on x86
   wine = callPackage ../misc/emulators/wine {
     wineRelease = config.wine.release or "stable";