xserver-common patching ideas:

- set DPI in separate variable instead of being part of ARGS
  + some devices needs only DPI setting
  + default ARGS are usually fine for devices

- use /etc/default/xserver for setting ARGS/DPI for new devices
  + no need to patch Xserver anymore
  + easy to tweak on device itself

- xmodmap stuff should be machine dependent so only one xmodmap is
  present on device

- zaurusd, devmand should provide session scripts instead of being
  called from Ts_calibrate script
