Invoke garbage collector?

[Sean Eskapp]

I'm having an unfortunate DSFML issue, where failing to free objects like
Images or Sprites causes exceptions to eventually be thrown. Calling the
built-in member dispose() causes access violations, so I assume it's not for
programmer use.

However, I need the resources to be freed more quickly than the GC is
apparently doing (I assume the Images and Sprites are eventually cleaned up),
so is there a way to invoke a GC cleanup in some way?