Use get_instance_handle() over GetModuleHandle(NULL)

[SamRodri]

See the winit discussion about this fix.

fixes #1445

• Tested on all platforms changed
• Compilation warnings were addressed
• cargo fmt has been run on this branch
• cargo doc builds successfully
• Added an entry to CHANGELOG.md if knowledge of this change could be valuable to users
• Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• Created or updated an example program if it would help users understand this functionality

[SamRodri]

I see that there is a major rewrite underway, maybe @kchibisov can copy this patch into his pull request?

[kchibisov]

Actually, I don't think I need this patch at all on my branch. I just need to use hinstance from the handle instead of that.

I'm not sure how I feel about adding this patch right now given that I'm unlikely to make a glutin release.

Is there a strong need for this patch or you can wait like a few more weeks and update to my rework given that it's nearly complete already?

[SamRodri]

No rush on my part, I can depend on my fork until your update is released.

[kchibisov]

Handled in #1435.