Since packed_cell and destroy_cell exist only to be queued, they go
in the same headers as the queues.

I was expecting this to be much worse.

This type is only used in one place and never exposed.

More modules use this than I had expected!

Now the entire connection_t hierarchy is extracted from or.h

For once, it's a type that is used almost nowhere else besides the
logical place.

This one was actually fairly simple.