We'll soon need the full apfl_ctx, where we previously only needed the
gc. apflc was the only place manually constructing a struct gc without
an apfl_ctx, so lets change that.
We're now first building a standalone bytecode compiler `apflc` that will
compile `globals.apfl` into bytecode and write it out as a C source file.
When initializing a new context, that embedded bytecode will then get
evaluated and the global scope will be populated from the dictionary
returned by that bytecode.
