fix process stdio when frozen as gui a executable

[Vizonex]

What do these changes do?

This change makes it so that tools like CX_Freeze can properly execute subprocesses in relation to bug #126

Are there changes in behavior for the user?

Problem solved. I just wanted to fix a couple of the last few bugs before we decomission winloop in the future and merge it to uvloop. Glad we fixed this though without screwing up more code in the process. We might need a way to close the handle when were done with it but I was able to reduce it to only leaking one handle if this is the case. Feel free to come up with a smarter PR for doing this that doesn't leak any handles. If winloop is decomissioned before then make the PR to uvloop and I will be there to help with the reviewing process.

Is it a substantial burden for the maintainers to support this?

Nope, uvloop contributors should be capable of understanding why this is here.

Related issue number

fixes #126

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes

[Vizonex]

@XiaoYouChR I hope this is what you expected. It may not be smart for me not to implement a CloseHandle but doing so just crashes the program hopefully someone smarter comes along to either winloop or uvloop later on and finds a smarter method for now I can finally rest. I might need someone to come up with a test but other than that, this case is successfully closed.