FOC: Use git for contrib preparation

Download Fiasco.OC/L4RE from our 'GitHub' fork. Deleted all patches.
FOC: SVN revision r42
foc_arndale: Added 'create_buildir' support
base-foc: Generate u-boot image if 'uboot' SPEC is set
Arndale: Build uImage, kernel, bootstrap
FOC: Change core's base address
FOC: Arndale kernel configuration
FOC: Use L2-cache synchronization calls

Replace L1 cache clean operations with L2 versions.
FOC: Add 'native_types' library

Make 'context_area_virtual_base' platform configurable.
FOC: Add 'uboot' spec to Arndale
cortex_a15: base/mk spec

(cherry picked from 'base_hw')
arndale: base/mk platform spec

(cherry picked from 'base_hw')
USB: Arndale EHCI controller support
FOC: SVN revision r47
USB: Move driver into library

This raised the opportunity to structure the library more cleanly for each
supported platform.