Update with latest PRs applied

see https://github.com/go-python/gopy/pulls?q=is%3Apr+is%3Aclosed for recent PRs applied.

-build-tags arg and GIL release

Thanks to @achals for -build-tags arg and @pyalex for GIL release while running Go functions.

-dynamic-link option added to link .so libs instead of static

Added by @pyalex:

"dynamic-link" (false by default) that changes flags used on linking stage (passed to ld).

When this flag is enabled instead of linking to python (via -l python3.x) we will use flags similar to what python itself uses during building extensions (see distutils.sysconfig.get_config_var("LDSHARED")). This allows packing the resulting .so / .dylib file into python package and distribute it via PyPi.

This has been already tested during publishing feast python package.

Support for variadic functions, .pyd files included

Thanks to @nishantsharma, variadic functions are now supported. Also .pyd files are included in the mainfest for setuptools, and the go tools version is updated to be compatible with go 1.18.

Significant updates for exe mode and windows working

Should be working a lot better all around..

Current stable release

well tested in extensive use for exe mode.

Release v0.3.0: pybindgen

ci: disable py2 in appveyor