Attached a patch that integrates generation into the build of python3.dll. There are also a couple of fixes for headers to retain functions/data that were previously exported.

The patch includes an updated python3.def file, though I expect that will go away and we'll check in the python3.txt file that is generated on build (which includes the return type). That way we can fail builds that modify the file (regardless of platform) and require an explicit step when adding to the stable API.

There are still a few functions towards the end of python3.def that I need to figure out how to deal with. (Also, my sort script doesn't quite match the result from however Serhiy sorted it last, but it's as close as I could get.)