In preparation for an ixp port, rename cpu/xscale and arch-xscale
into cpu/pxa and arch-pxa.

  - fix bug in BOOTP code (must use NetCopyIP)
  - update of CSB226 port
  - clear BSS segment on XScale
  - added support for i2c_init_board() function
  - update to the Innokom plattform

* Extend support for redundand environments for configurations where
  environment size < sector size