Install header files in xserver's sdk dir.
Install header files in xserver's sdk dir.

Missing from 851097c45f02f2a033975cd3b2ed9490a4aa87bd. Don't install header
files in <prefix>/include, install them in <prefix>/include/xorg instead.

mildred/xorg-synaptics-orientation-patch,corcoran/xserver-xorg-input-synaptics,Lyude/xf86-input-synaptics,joeshaw/xf86-input-synaptics,ssaavedra/xf86-input-synaptics,quadpixels/three-finger-dragging,mmonaco/xf86-input-synaptics,RazZziel/synaptics-xrandr,mmonaco/xf86-input-synaptics,sencer/synaptics,gdestuynder/xf86-input-synaptics,kelnos/xf86-input-synaptics,RsrchBoy/xserver-xorg-input-synaptics,felipejfc/xserver-xorg-input-synaptics,quadpixels/three-finger-dragging,Lyude/xf86-input-synaptics,mildred/xorg-synaptics-orientation-patch,kelnos/xf86-input-synaptics,eyko/xf86-input-synaptics,philipn/xserver-xorg-input-synaptics,felipejfc/xserver-xorg-input-synaptics,gdestuynder/xf86-input-synaptics,mortehu/xf86-input-synaptics,joeshaw/xf86-input-synaptics,philipn/xserver-xorg-input-synaptics,nanderson94/xf86-input-synaptics,eyko/xf86-input-synaptics,RsrchBoy/xserver-xorg-input-synaptics,ssaavedra/xf86-input-synaptics,jiixyj/xf86-input-synaptics,RazZziel/synaptics-xrandr,jiixyj/xf86-input-synaptics,philipn/xserver-xorg-input-synaptics,sencer/synaptics,nanderson94/xf86-input-synaptics,corcoran/xserver-xorg-input-synaptics,felipejfc/xserver-xorg-input-synaptics,mortehu/xf86-input-synaptics