message: Expose FrozenHeap from Freezer
  Summary: Needed later, but might be helpful anyway.
diff: @@ -387,6 +387,13 @@ impl Freezer {
  Either::Right(v) => unsafe { v.heap_freeze(self) },
  }
  }
  +
  + /// Frozen heap where the values are frozen to.
  + ///
  + /// Can be used to allocate additional values while freezing.
  + pub fn frozen_heap(&self) -> &FrozenHeap {
  + &self.heap
  + }
  }
  impl Heap {
  