==== Enable Mouse Wheel Emulation Automagically for ANY Mouse ====
Edit the following section of `/etc/X11/xorg.conf.d/10-evdev.conf`
<code>
Section "InputClass"
        Identifier "evdev pointer catchall"
        MatchIsPointer "on"
        MatchDevicePath "/dev/input/event*"
        Driver "evdev"
        Option      "EmulateWheel"      "true"
        Option      "EmulateWheelButton"    "2"
        Option      "XAxisMapping"      "6 7"
        Option      "YAxisMapping"      "4 5"
EndSection
</code>

References:

  * https://bbs.archlinux.org/viewtopic.php?id=133298