add missing win32 constant for old win sdk

Zhao Yuhang

2025-03-11 c00e986f38dbc4843d92cc76a385f826658c1e03

 src/core/contexts/win32windowcontext_p.h

@@ -73,7 +73,9 @@
        // WM_MOUSELEAVE.
        bool mouseLeaveBlocked = false;

        // For emulating traditional icon button behavior
        uint64_t iconButtonClickTime = 0;
        int iconButtonClickLevel = 0;
    };

}