The new gg format is based on a BNF file which can be found in the `gg`
directory. The code for decoding `.gg` files has been refactored to
mirror that file. The result is more resilient parsing, better errors,
and a greater ability to extend the format in the future.
The new decoder is notable in that it does not use a lexer. Both lexing
and parsing are done in a single step.
The format syntax itself has also been modified. Rather than using
semi-colons everywhere, commas are used as separators in tuples.
Additionally the final comma/semi-colon is no longer required.
This commit is the result of many days of picking vm apart and putting
it back together again. The result is an implementation which separates
compile and runtime into separate steps, and which functions (more)
correctly in the face of recursion.
Pretty much all aspects of vm have been modified or deleted, so it's not
even really worth it to describe specific changes. Just pretend this is
the original implementaiton and the old one was never done.
