I finally managed to compile the driver. I had to add the location of the above header files to the make file (this headers ara not included in x11-devel but I took them from the sources of xorg-6.9.0).
make compiled the driver without errors. make install installed it into a different directory. I copied the evtouch_drv.so file to
startx gives me this message
(EE) LoadModule: Module evtouch does not have a evtouchModuleData data object.
(II) UnloadModule: "evtouch"
(II) Unloading /usr/X11R6/lib/modules/input/evtouch_drv.so
(EE) Failed to load module "evtouch" (invalid module, 0)
This driver really gives me some headache.