db: Reorganize Berkeley Database Packaging

Currently, the berkeley databases resuses a lot of the same code for the
expressions of each version. This consolidates all of the build routines
similar to that of the linux kernel.

This patch also adds version 6 of BDB.

pkgs/development/libraries/db/db-5.3.nix

@@ -1,32 +1,6 @@
-{ stdenv, fetchurl
-, cxxSupport ? true
-}:
+{ stdenv, fetchurl, ... } @ args:
 
-stdenv.mkDerivation rec {
-  name = "db-5.3.28";
-
-  src = fetchurl {
-    url = "http://download.oracle.com/berkeley-db/${name}.tar.gz";
-    sha256 = "0a1n5hbl7027fbz5lm0vp0zzfp1hmxnz14wx3zl9563h83br5ag0";
-  };
-
-  configureFlags = [
-    (if cxxSupport then "--enable-cxx" else "--disable-cxx")
-  ];
-
-  preConfigure = ''
-    cd build_unix
-    configureScript=../dist/configure
-  '';
-
-  postInstall = ''
-    rm -rf $out/docs
-  '';
-
-  meta = with stdenv.lib; {
-    homepage = "http://www.oracle.com/technetwork/database/database-technologies/berkeleydb/index.html";
-    description = "Berkeley DB";
-    license = "Berkeley Database License";
-    platforms = platforms.unix;
-  };
-}
+import ./generic.nix (args // rec {
+  version = "5.3.28";
+  sha256 = "0a1n5hbl7027fbz5lm0vp0zzfp1hmxnz14wx3zl9563h83br5ag0";
+})