Adding ghdl 0.31 mcode flavour

This allows having a recent ghdl, without building it with gcc.
The major drawback is the speed.

pkgs/development/compilers/ghdl/default.nix

@@ -0,0 +1,64 @@
+{ stdenv, fetchurl, gnat, zlib }:
+
+assert stdenv.system == "i686-linux";
+
+let
+  version = "0.31";
+in
+stdenv.mkDerivation rec {
+  name = "ghdl-mcode-${version}";
+
+  src = fetchurl {
+    url = "mirror://sourceforge/ghdl/ghdl-${version}.tar.gz";
+    sha256 = "1v0l9h6906b0bvnwfi2qg5nz9vjg80isc5qgjxr1yqxpkfm2xcf0";
+  };
+
+  buildInputs = [ gnat zlib ];
+
+  # Tarbomb
+  preUnpack = ''
+    mkdir ghdl
+    cd ghdl
+  '';
+
+  sourceRoot = "translate/ghdldrv";
+
+  patchPhase = ''
+    sed -i 's,$$curdir/lib,'$out'/share/ghdl_mcode/translate/lib,' Makefile
+  '';
+
+  postBuild = ''
+    # Build the LIB
+    ln -s ghdl_mcode ghdl
+    make install.mcode
+  '';
+
+  installPhase = ''
+    ensureDir $out/bin
+    cp ghdl_mcode $out/bin
+
+    ensureDir $out/share/ghdl_mcode/translate
+    cp -R ../lib $out/share/ghdl_mcode/translate
+    cp -R ../../libraries $out/share/ghdl_mcode
+
+    ensureDir $out/share/man/man1
+    cp ../../doc/ghdl.1 $out/share/man/man1/ghdl_mcode.1
+
+    # Ghdl has some timestamps checks, storing file timestamps in '.cf' files.
+    # As we will change the timestamps to 1970-01-01 00:00:01, we also set the
+    # content of that .cf to that value. This way ghdl does not complain on
+    # the installed object files from the basic libraries (ieee, ...)
+    pushd $out
+    find . -name "*.cf" -exec \
+        sed 's/[0-9]*\.000" /19700101000001.000" /g' -i {} \;
+    popd
+  '';
+
+  meta = {
+    homepage = "http://sourceforge.net/p/ghdl-updates/wiki/Home/";
+    description = "Free VHDL simulator, mcode flavour";
+    maintainers = with stdenv.lib.maintainers; [viric];
+    platforms = with stdenv.lib.platforms; linux;
+    license = "GPLv2+";
+  };
+}

pkgs/top-level/all-packages.nix

@@ -2732,6 +2732,8 @@ let
     enableMultilib = false;
   });
 
+  ghdl_mcode = callPackage ../development/compilers/ghdl { };
+
   gcl = builderDefsPackage ../development/compilers/gcl {
     inherit mpfr m4 binutils fetchcvs emacs zlib which
       texinfo;