Allow building kcminput without libusb-compat
Review Request #124275 - Created July 6, 2015 and submitted
|apol, davidedmundson, graesslin|
Some distros are slowly targetting to get rid of the old libusb (see discussion in http://lists.opensuse.org/opensuse-factory/2015-07/msg00158.html)
As the code mouse.[cpp,h] and logitechmouse.[cpp,h] is already ready for such an option, allow cmake to recognize this also.