ocaml-cairo: fix sha256

Seems that the original sha was just wrong but because Hydra doesn't
build this and we appear to have had no OCaml users until very recently,
no one noticed.

pkgs/development/ocaml-modules/ocaml-cairo/default.nix

@@ -1,4 +1,4 @@
-{stdenv, fetchurl, automake, ocaml, autoconf, gnum4, pkgconfig, freetype, lablgtk, unzip, cairo, findlib, gdk_pixbuf, glib, gtk, pango }: 
+{stdenv, fetchurl, automake, ocaml, autoconf, gnum4, pkgconfig, freetype, lablgtk, unzip, cairo, findlib, gdk_pixbuf, glib, gtk, pango }:
 
 let
   ocaml_version = (builtins.parseDrvName ocaml.name).version;
@@ -9,21 +9,22 @@ in
 stdenv.mkDerivation {
   name = "${pname}-${version}";
 
-  src = fetchurl { 
+  src = fetchurl {
     url = "http://cgit.freedesktop.org/cairo-ocaml/snapshot/cairo-ocaml-${version}.zip";
-    sha256 = "2d59678e322c331e3f4bc02a77240fce4a0917acb0d3ae75953a6ac62d70a125";
+    sha256 = "0l4p9bp6kclr570mxma8wafibr1g5fsjj8h10yr4b507g0hmlh0l";
   };
 
   patches = [ ./META.patch ];
 
-  buildInputs = [ocaml automake gnum4 autoconf unzip pkgconfig findlib freetype lablgtk cairo gdk_pixbuf gtk pango ];
+  buildInputs = [ ocaml automake gnum4 autoconf unzip pkgconfig
+                  findlib freetype lablgtk cairo gdk_pixbuf gtk pango ];
 
   createFindlibDestdir = true;
 
  preConfigure = ''
    aclocal -I support
    autoconf
-   export NIX_CFLAGS_COMPILE="$NIX_CFLAGS_COMPILE `pkg-config --cflags cairo gdk-pixbuf glib  gtk+ pango`" 
+   export NIX_CFLAGS_COMPILE="$NIX_CFLAGS_COMPILE `pkg-config --cflags cairo gdk-pixbuf glib gtk+ pango`"
    export LABLGTKDIR=${lablgtk}/lib/ocaml/${ocaml_version}/site-lib/lablgtk2
    cp ${lablgtk}/lib/ocaml/${ocaml_version}/site-lib/lablgtk2/pango.ml ./src
    cp ${lablgtk}/lib/ocaml/${ocaml_version}/site-lib/lablgtk2/gaux.ml ./src
@@ -39,6 +40,6 @@ stdenv.mkDerivation {
     homepage = http://cairographics.org/cairo-ocaml;
     description = "ocaml bindings for cairo library";
     license = stdenv.lib.licenses.gpl2;
-#    maintainers = [ stdenv.lib.maintainers.roconnor ];
+    platforms = stdenv.lib.platforms.linux;
   };
 }