shutter: wrap XDG_DATA_DIRS with hicolor-icon-theme

When opening `shutter` it adds an indicator icon to the status bar.
However this doesn't happen (and an ugly default icon will be used) if
`shutter` can't find the `hicolor-icon-theme`. In such a case a warning
like this can be found in `stderr`:

```
Gtk-WARNING **: Could not find the icon 'image-png'. The 'hicolor' theme
was not found either, perhaps you need to install it.
```

As I don't think that we should force users to install this theme
globally and several other packages including `tor-browser`, `gparted`
or `clawsmail` add `hicolor-icon-theme` to their closure this seems to
be a fair measure.

pkgs/applications/graphics/shutter/default.nix

@@ -1,4 +1,6 @@
-{ stdenv, fetchurl, fetchpatch, perl, perlPackages, makeWrapper, imagemagick, gdk_pixbuf, librsvg }:
+{ stdenv, fetchurl, fetchpatch, perl, perlPackages, makeWrapper, imagemagick, gdk_pixbuf, librsvg
+, hicolor-icon-theme
+}:
 
 let
   perlModules = with perlPackages;
@@ -29,6 +31,7 @@ stdenv.mkDerivation rec {
     wrapProgram $out/bin/shutter \
       --set PERL5LIB "${stdenv.lib.makePerlPath perlModules}" \
       --prefix PATH : "${imagemagick.out}/bin" \
+      --suffix XDG_DATA_DIRS : "${hicolor-icon-theme}/share" \
       --set GDK_PIXBUF_MODULE_FILE "$GDK_PIXBUF_MODULE_FILE"
   '';