lang: Free modules after loading is finished

Bump copyright year

lang: Create modules and dependencies on request

lang: Print all done when main is finished

lang: Add code to find a module by its name

lang: Add a second module as a test

lang: Add multiply and divide and rational loop test

lang: Change rational_value to rational_integer

lang: Rename number to rational

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: Add looping test

lang: Add simple If statements

lang: Use object_none() instead of NULL

lang: Add None objects to the language

lang: Add booleans

lang: Replace func with dynamically compiled module ...

I did some tweaking to the style of the generated bytecode but otherwise
this is basically merging func.c in to compile.py. Seems to work for now.

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

lang: Fix typo

lang: Check values since we're kind of testing anyway

lang: Always place VmState first in function calls

lang: Add opaque types for Object and VmState

lang: Handle vm_state creation in vm

lang: Switch to callee cleanup of non-return arguments ...

This simplifies calling things and will allow proper tail calls.

lang: Create vm state once in main

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