Added support for cursor visibility in WinForms.

[proneon267]

Added support for cursor visibility in WinForms for the existing APIs. As discussed, implementation was done under existing API and no new API was added. A shadow variable was needed as the calls to show and hide cursor needs to be balanced.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[proneon267]

@freakboy3742 Does this need some changes, or is it good?

[freakboy3742]

This is on my list to look at; however, given the issues with #1895, I want to actually test this myself on Windows before merging, and I won't get a chance to do that until I'm back at work next week.

[proneon267]

This is on my list to look at; however, given the issues with #1895, I want to actually test this myself on Windows before merging, and I won't get a chance to do that until I'm back at work next week.

Thanks. Take your time :)

[freakboy3742]

I've added a manual test case, but otherwise this looks good.

[proneon267]

I've added a manual test case, but otherwise this looks good.

Thanks :)