Handle XF86TouchpadToggle event

Submitted by haarp

Assigned to Nick Schermer

Link to original bug (#10223)

Description

This event is used on some laptops to toggle the touchpad on and off. It is currently completely unhandled in Xfce, requiring the use of custom scripts.

It should give a short notification and then disable/enable the touchpad.

Additionally, Synaptics touchpads can also set TouchpadOff=2, which only disables scrolling and tapping. This could also be included (on -> tapping/scrolling off -> all off -> on, etc)

Version: 4.10.1