By "stats" I mean the internal numbers gathered by the VM for performance and debugging. This has nothing to do with any statistics module.

Currently various parts of the VM gather stats: the GC, dicts, the bytecode interpreter, type lookup cache, etc.

These stats have various compile time flags to turn them on and off. They have differing ways to display the stats, and no unified way to gather stats across different runs.

For the specialization stats we dump stats, which we can parse to collate stats across runs.

We should:
1. Add a --with-pystats config flag (like with-pydebug) to turn on stat gathering at build time.
2. Convert the other stats to the format used by the specialization stats, so all stats can be parsed and collated.