Implement symbol table for Scheme code generation

[hawkw]

Implement symbol table for Scheme code generation

[hawkw]

Because of the way scopes work on the VM, I'm not entirely sold on the ForkTable as it currently stands as the right way to figure out scopes. Considering that the primary function of the scoping system is to figure out indices into the environment on the VM, there might be a need to change the scoping algorithm in the compiler. I'm reopening this, since I think there's still some scoping stuff to figure out.