[rc] add toggle-tablet script for use with my X220t

This script toggles between a 'normal' mode and a 'tablet' mode, doing
a few things:

- rotates the screen using xrandr, so that rotating the physical
  display of my X220t would have the laptop's battery on the right
  hand side,
- enables touch screen,
- properly rotates the stylus pen and touch screen pointers, and
- toggles between RGB and Vertical BGR sub-pixel order.