napi: add napi_env to napi_get_last_error_info()

[gabrielschulhof]

This makes it necessary to pass napi_env to napi_get_last_error_info()
thereby ensuring that errors can be tied to the napi_env in the future.

Re #198

[jasongin]

should napi_get_last_error_info return a napi_status

I'm leaning toward yes, both for consistency with other APIs and so that it can return an error code if you pass it a null/invalid env. The alternative is to indicate an error via a null return value, but I don't like that as much.

[jasongin]

You'll need to rebase and merge after my last change. Sorry.

[jasongin]

I rebased and pushed a commit to @gabrielschulhof's branch.

[jasongin]

CI passed: https://ci.nodejs.org/view/x%20-%20Abi%20stable%20module%20API/job/node-test-commit-linux-abi/120/

[gabrielschulhof]

@jasongin @boingoing thanks for jumping in!