[PATCH 0/1] MR2880: win32u: Propagate WM_MOUSEHWHEEL to the parent window in DefWindowProc().

[Brendan Shanks (＠bshanks)]

This enables horizontal scrolling gestures/wheels (tested on macOS) in applications like IrfanView which handle WM_MOUSEHWHEEL.
Support will need to be added to common controls for horizontal scrolling to work in programs like Wine's explorer or regedit.