Show mouse refresh rate under linux + evdev

For information about polling rate, see
https://wiki.archlinux.org/index.php/Mouse_Polling_Rate

Note: There exists a kernel bug for USB ports which use the uhci_hcd 
driver, where a 1000 hz mouse will only read at 500hz, causing 
jittering. A workaround is to use USB ports that use the ehci-pci 
driver. See
  https://bugzilla.kernel.org/show_bug.cgi?id=60586