gpython: Preimport golang and gevent from exactly the same place as std python would do
GPython preimports golang and gevent, but until now, it was preimporting them before adjusting sys.path according to given -c/-m/file/... And this was leading to difference in behaviour with standard Python where e.g. `import golang` might result in different files loaded if e.g. golang/ is there on cwd and -c/-m was given. -> Rework gpython startup so that golang/gevent preimport happens after sys.path initialization. This fixes `tox -e py27-gevent` which was previously failing on test_defer_excchain_dump_pytest / test_defer_excchain_dump_ipython because dumped paths were different than expected ones. It, however, breaks test_defer_excchain_traceback on py27-gevent. -> We'll do more fixups to sys.path handling in the next patch which will fix that failure as well.
Showing with 47 additions and 36 deletions