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
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.
Fixed some unused parameters warnings

They cause problems when using -Werror in your compilation.
base-linux: Don't busywait if lx_pollpid returns 0

This happened when I killed one of the genode clients which was
tracked via an expception_handler. In this case the wait4 syscall
returned 0 and the for(;;) was looped eternally. This caused an
100% CPU utilization for the core binary.
Add the 'cxx' lib in base.mk for 64-bit Linux

This is a follow-up fix for fae63f4fa9df237a5fa3d658b870def17e82f265.
Thanks to Christian Prochaska for the patch.