lang: Fix tail calls not dispatching on object_none

lang: Convert vm to use an object_list

lang: Mark tail_obj as not a pointer

lang: Clean up one-line if statements

lang: Use calloc for vm_create

lang: Free the VM stack trace

lang: Add debug logging

lang: Add stack traces on abort

lang: Move abort_msg and abort_if to vm

lang: Pass VmState to abort

lang: Couple object functions to VmState ...

This is needed for coupling abort() to VmState and stack traces.

lang: Check for malloc failure

lang: vm: Check stack malloc failure

lang: Add jumps (tail calls) ...

This isn't the cleanest implementation but it works.

lang: Abort if vm_stack_drop is too small

lang: Add a 'none' object to replace NULL uses

lang: Check stack depth before accessing elements ...

I tested this code by hand, make sure to do the same if changing.

lang: Always place VmState first in function calls

lang: Remove arg_count and rely on stack depth instead

lang: Hide VmState internals

lang: Add opaque types for Object and VmState

lang: Use stack offsets instead of pointers

lang: Handle vm_state creation in vm

lang: Add back reference counting ...

The basic idea here is that we transfer ownership to and form the stack,
and clean up references that way.

vm: Add stack pushing and popping

lang: Rename vm.stack to vm.stack_next

lang: Add stack bases to vm

lang: Drop reference counting, embrace leaking ...

I will add proper garbage collection later

lang: Wrap stack functions

lang: Replace args with a vm_state stack ...

This doesn't have any functional changes at the moment but will
aid in adding proper stack support in the future.