SDL2: cleanup and add patch to discover extensions

pkgs/development/libraries/SDL2_image/default.nix

@@ -1,27 +1,20 @@
 { stdenv, fetchurl, SDL2, libpng, libjpeg, libtiff, libungif, libXpm, zlib }:
 
 stdenv.mkDerivation rec {
-  name = "SDL2_image-2.0.1";
+  name = "SDL2_image-${version}";
+  version = "2.0.1";
 
   src = fetchurl {
     url = "http://www.libsdl.org/projects/SDL_image/release/${name}.tar.gz";
     sha256 = "0r3z1l7fdn76qkpy7snpkcjqz8dkv2zp6lsqpq25q4m5xsyaygis";
   };
 
-  buildInputs = [SDL2 libpng libjpeg libtiff libungif libXpm zlib];
+  buildInputs = [ SDL2 libpng libjpeg libtiff libungif libXpm zlib ];
 
-  postInstall = ''
-    sed -i -e 's,"SDL.h",<SDL2/SDL.h>,' \
-      -e 's,"SDL_version.h",<SDL2/SDL_version.h>,' \
-      -e 's,"begin_code.h",<SDL2/begin_code.h>,' \
-      -e 's,"close_code.h",<SDL2/close_code.h>,' \
-      $out/include/SDL2/SDL_image.h
-    ln -sv SDL2/SDL_image.h $out/include/SDL_image.h
-  '';
-
-  meta = {
+  meta = with stdenv.lib; {
     description = "SDL image library";
     homepage = "http://www.libsdl.org/projects/SDL_image/";
-    platforms = stdenv.lib.platforms.linux;
+    platforms = platforms.linux;
+    license = licenses.zlib;
   };
 }