This directory contains all the AST Node classes used by the
compiler. Most of them inherit from an equivalent Ruby Node class
defined in rbx's lib/compiler/ directory.

Each node class has a bytecode() method in which the actual bytecode
generation is done by calling generator methods on the generator
object, that is passed in as an argument.

If there's no bytecode() method defined in a node class, this just
means, we're simply using the bytecode() method of the superclass (the
one defined by rbx's compiler library).