[Buildroot] x11 and touch screen calibration

[Yegor Yefremov]

I have a 8" resistive touch screen. The whole stuff is working but
rather inaccurate. ts_calibrate and ts_test give good results and
after patching Android to use pointercal file I have no problems
either.

How do I get X11 to use the values from /etc/pointercal? For now I'm
using fluxbox, but I'm also open to other managers.

Yegor