fix cursor blinking when clicking decorations bar on Windows

[Ssaely]

On Windows when clicking on the decorations bar the mouse cursor would briefly blink. This PR fixes this by passing in the LPARAM received in the WM_NCLBUTTONDOWN when posting the message

• 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
• Updated feature matrix, if new features were added or implemented

[maroider]

The issue this fixes is something that's been bothering me a bit, but not enough for me to investigate it myself.

I'll admit that I don't quite understand why there's a PostMessage call there in the first place, but I can't really be bothered to chase it through git blame either.

So, thanks for saving me the work :D

[Ssaely]

I'll admit that I don't quite understand why there's a PostMessage call there in the first place

I honestly wasn't sure why that was there either and thought about completely removing that, but after some digging I found this, which was the PR where a custom handler for WM_NCLBUTTONDOWN was originally created.