Add a powerpc uclibc toolchain

Change-Id: Ib3ab916bf2651ac11199b06e1c5123213addf3fd
Signed-off-by: Alban Bedel <albeu@free.fr>
Reviewed-on: http://review.adnet.avionic-design.de/317
Reviewed-by: Soeren Grunewald <soeren.grunewald@avionic-design.de>