feature request: remove the jna dependency

[PiprTuff]

The JNA dependency is now redundant. It should be removed.

[dialex]

For future reference, (as I keep returning to this issue and forget what's the current state), here's some context.

The JNA dependency was introduced because of this: Windows 10 users assumed JColor didn't work, but in fact it was a limitation of Windows. The JNA allowed us to change a Windows default without the user noticing, so that JColor works as expected.

Later on, I decided to stop doing that for the users, so that I could remove the JNA dependency and keep this library lean. So now Windows 10 users already have to fix this by themselves, and I made a detailed list of workarounds and instructions.

At this point, the only thing missing is removing the dependency, because the code that used that dependency was already removed. I'll create a PR to clean that up once and for all.

Thanks for reminding me about this 😉