feat: Added support for horizontal scrolling on Windows

[metamemelord]

Summary

Add support for Horizontal scroll on Windows by capturing the WM_MOUSEHWHEEL event.

Changes

Capture WM_MOUSEHWHEEL event and then relay it to the client.

To test

• Connect a mouse with horizontal scroll wheel (e.g. Dell MS900, Logitech MX) to the server
• Move cursor to a client machine
• Scroll horizontally on a wide spreadsheet or a large page that is horizontally scrollable.

Testing

Tested working on 2 windows machines (Kerberos - server, Surface-Studio - client)

• Log file: Synergy.log
• Pastebin link with same logs (for security concerns with downloading the logfile): https://pastebin.com/2zu6U0Bw

I see DEBUG1 statements, onMouseWheel working with both x, y for horizontal, vertical scroll respectively.

[2026-03-27T14:45:24] DEBUG1: event: button wheel delta=-120,+0
[2026-03-27T14:45:24] DEBUG1: onMouseWheel -120,+0
[2026-03-27T14:45:24] DEBUG1: event: button wheel delta=+0,+120
[2026-03-27T14:45:24] DEBUG1: onMouseWheel +0,+120