Still pretty horribly broken. I was generating dispacements
backwards, failing to emit stuff like the beginning of
loops, the logic for `if` jumps was backwards, etc.
I was also completely forgetting to increment file_here
for appends. I don't remember what all I did; check the diff.
Now we always use the stack instead of keeping a TOS register.
This is very inefficient, but I'll worry about register
allocation later.
The new block model is inspired by x86's `enter` and `leave`
instructions. I intend to support nested procedures at some point
in the future.
James T. Martin