complibs/ppl: build watchdog library

gcc-4.6+ requires the Parma Watchdog Library (libpwl).
Build it and use it.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

reporter_name="Julien DUSSER"

reporter_url="http://sourceware.org/ml/crossgcc/2008-10/msg00054.html"

reporter_comment="Soft-float for the 405 PowerPC"