nixos/virtualbox-image: Use 32MB of video memory.

Booting the demo/installer image won't work if the video memory is too
low. It boots into KDE, shows the background image and doesn't do
anything, according to @domenkozar.

Thanks to @domenkozar for reporting and testing this with 32MB.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

nixos/modules/virtualisation/virtualbox-image.nix

@@ -109,7 +109,7 @@ in {
         VBoxManage createvm --name "$vmName" --register \
           --ostype ${if pkgs.stdenv.system == "x86_64-linux" then "Linux26_64" else "Linux26"}
         VBoxManage modifyvm "$vmName" \
-          --memory 1536 --acpi on --vram 10 \
+          --memory 1536 --acpi on --vram 32 \
           ${optionalString (pkgs.stdenv.system == "i686-linux") "--pae on"} \
           --nictype1 virtio --nic1 nat \
           --audiocontroller ac97 --audio alsa \