64-bit fixes

Fixes #734.
Simplify GPIO session interface (fix #707)

Changes GPIO session interface to a one-GPIO-pin-per-session style. Moreover,
this commit introduces a generic driver interface for GPIO drivers. Thereby
generalizes root- and session component for GPIO.
Implement input driver for i.MX53 tablet (fix #724)

The input driver implements support for the Egalaxy touchscreen and
for Freescale's MPR121 capacitative touch buttons.