Basic out of order compilation

[stevehalliwell]

Presently the compiler expects to be fed elements in the order they are required. As projects get larger this becomes more of a unwanted burden.

A starting improvement here might to be compile a chunk at a time, if a chunk fails to compile due to external name not found. It aborts the chunk, orders itself at the bottom of the compile queue and compilation continues. We could detect compile stall outs by tracking the last reported error from the items in the compile queue, if a full iteration of it results in exactly the same errors in each we are stalled.

Another option would be to look back at c and introduce forward declare concept, a trust me, this thing will exist. In cases where that would be a direct bind to a chunk/closure that's just going to require a later patch up.