Remove importing C from conversions.go

[hajimehoshi]

This is one of the steps in order to remove dependency on Cgo on Windows (go-gl/gl#109).

[hajimehoshi]

@dmitshur Could you take a look? Thanks!

[dmitshur]

It's hard for me to know what effect making this change would have, and I'm hesitant to make a change here before knowing the full picture.

Have you already prototyped the entire "drop Cgo" change for Windows, or is this just a beginning?

I'm worried about what happens if the rest of the changes don't work out, and we'll have made this change without going all the way through.

[dmitshur]

Also, any non-trivial changes to glow make sense to land after we've gained confidence in the generated code works well and we want to keep it.

[hajimehoshi]

Have you already prototyped the entire "drop Cgo" change for Windows, or is this just a beginning?

Sorry but it is just a beginning. I'm 90% sure I can do though, and even if it was not possible, I thought removing Cgo dependency as much as possible was always good. But, you are right, we need to confirm that everything works.

I'll make the entire change first, and split them into chunks. Thank you for your advice.