Bug#866590: xfce4-settings: Touchpad config options not visible

[JCGoran <jcgoran@protonmail.com>]

Dear Maintainer,

This bug is still present on Debian Sid (version 4.14.2-1).
I suspect this is because xfce4-settings doesn't have the libinput10 
package as a direct dependency (or xserver-xorg-input-libinput, not sure 
which one is relevant here), and the xfce4-settings source code contains 
a bunch of #ifdefs that depend on the presence of libinput, so if the 
headers aren't included during compile time, libinput-specific options 
won't be enabled in the final binary.
Of course, one could always manually compile it from source with 
xserver-xorg-libinput-dev installed, but, seeing as how the Synaptics 
driver is deprecated, and Xorg is required to run Xfce, I think it'd be 
a good idea to include it as a dependency.

Thanks for reading,
Goran