[DGD] Enabling/disabling closures

[Raymond Jennings]

Anyone using closures, just got hit by a small gotcha.

If you enable them during a compilation of DGD, and then you create a
snapshot with it, you'll have to use the "use a debugger to flush out the
unused kfuns" thing before you can turn it off.

I tried to use a no-closures compile of DGD to restore a closures enabled
snapshot and it gave me an error, so be careful.